So, that 31st January 2027 deadline for your 2025/26 Self Assessment? Yeah, it feels like forever, doesn't it? But honestly, HMRC isn't exactly known for being super understanding if you're late. They're not. let's be honest — and you'd be amazed how many people get caught out, thinking they don't even need to file one this year. Are you sure you're not one of them?
This guide will walk you through what you'll need for the 2025/26 tax year. It's something that catches a surprising number of people off guard when they first encounter it, which is something that catches a surprising number of people off guard when they first encounter it. From figuring out if you even need to file, to dealing with the online submission. arguably, that matters.
And understanding those very important deadlines. It's all here, every last bit. (which, frankly, seems excessive) I've seen it all, believe me. Just last week, a client, bless her heart, thought her P800 was a lottery win, and that's before you even factor in the additional complications that arise from the interaction with other reliefs and allowances. the thing is — but no, darling, just HMRC saying you owe them more.
Understanding your tax obligations isn't just about ticking boxes, oh no. It's about smart financial planning, pure and simple. By knowing what you can legitimately claim and when you need to act, you can dodge those ghastly penalties, though the practical reality of how this works in practice is rather more complicated than the headline figure might suggest. it seems to me, it seems to me, that matters.
Honestly, who doesn't want to pay less tax? It's all about making sure your tax bill is as small as it can possibly be — and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. Simple as that.
Honestly, this is such a lifesaver for your money stuff — and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. To be fair, it just makes everything so much tidier, doesn't it? No more scrambling around, wondering where things are. here's the rub — so simple.
Who Needs to File?
Right, so Self Assessment. It's basically how HMRC gets its income tax from people who aren't having it all taken straight from their wages through PAYE — and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. Most folks who are employed won't ever need to bother with it, which is nice.
But, there are loads of reasons why you might. You absolutely have to send one in for the 2025/26 tax year if any of these things apply to you, which is something that catches a surprising number of people off guard when they first encounter it.
Got it?
* Self-employed individuals: If you were a sole trader, and your gross income sailed past £1,000. That's before taking off any allowances, mind. Even if your income fell below £1,000, you might still choose to file. Perhaps to claim expenses or reliefs, of course. * Partners in a business partnership: Every single partner, income level despite, must complete a Self Assessment return. There are no exceptions to this rule. * Company directors: This applies unless you're a non-salaried director of a non-profit outfit. A charity, say. And you've no other income that screams Self Assessment. * Individuals with steep untaxed income: This includes money from renting out property. Even if you're a landlord with just one little flat. Or freelance work. Or commissions. If the gross income is over £1,000, it's on the list. * Individuals receiving foreign income: If you live here in the UK and have income from abroad. Or live abroad and have UK income. And that income isn't taxed in the UK. * Those claiming Child Benefit where one partner earns over £50,000: The High Income Child Benefit Charge (HICBC) kicks in here. Honestly, it demands a Self Assessment return. So you'll repay some, or all, of the Child Benefit. * Individuals with income from savings, investments, or dividends: If your income from these sources is rather chunky. And not taxed at source. Or it exceeds your personal allowances. Say, if your dividend income goes beyond the £500 dividend allowance (likely £500 for 2025/26). Or savings interest exceeds your Personal Savings Allowance. * Individuals making capital gains: If you sold an asset. Perhaps a second home. Or shares not tucked away in an ISA. And you made a profit above the annual exempt amount (expected to be £3,000 for 2025/26). You'll need to report this. * Those needing to pay National Insurance contributions: Such as if you're self-employed and need to pay Class 2 and Class 4 NICs. * Individuals who received a P800 from HMRC: If HMRC sent you a P800 tax calculation. And it clearly stated you need to pay tax. * Trustees: If you're a trustee of a trust or a registered pension scheme. * Ministers of religion. * Anyone who needs to claim tax reliefs or expenses: Even if not strictly mandatory, filing can be a clever move. to be fair, it lets you claim back overpaid tax. Or benefit from reliefs like Gift Aid.
Still feeling a bit wobbly? Best to check with HMRC or a proper tax advisor — and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. Ignoring a filing requirement can land you in hot water. Penalties are no joke.
Key Deadlines for 2025/26
Look, you absolutely have to hit those deadlines. Seriously. Miss 'em, and HMRC will just slap you with fines, which is a real pain, isn't it? And here's the kicker, something that always throws people: the 2025/26 tax year actually kicks off on 6 April 2025 and runs all the way to 5 April 2026. It's a bit weird, I know. But that's how it works.
| Action | Deadline (2025/26 Tax Year) | Penalties for Missing Deadline |
|---|---|---|
| Register for Self Assessment | 5 October 2026 | £100 if late, plus further penalties |
| Paper Tax Return submission | 31 October 2026 | £100 if 3 months late, then increasing |
| Online Tax Return submission | 31 January 2027 | £100 if 3 months late, then increasing |
| Pay Tax Bill for 2025/26 | 31 January 2027 | 5% surcharge on unpaid tax after 30 days, plus interest |
| 1st Payment on Account for 2026/27 | 31 January 2027 | Interest charged on late payments |
| 2nd Payment on Account for 2026/27 | 31 July 2027 | Interest charged on late payments |
Plus, it covers your first payment on account for the 2026/27 tax year — and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. Missing these deadlines can trigger automatic penalties. And interest charges. honestly, these can quickly spiral, believe me.
Step-by-Step Filing Process
Honestly, doing your Self Assessment? It's like trying to scale Everest in flip-flops, isn't it? (not always straightforward, admittedly) But look, it doesn't have to be a total nightmare. Just breaking it down into smaller, bite-sized chunks makes it so much less daunting – and if you've ever wrestled with HMRC's forms yourself, you'll totally get what I'm saying. It's a pain.
Register for Self Assessment — if you haven't already — : If you're self-employed, register pronto after starting your business. If you need to file for other reasons, register by 5 October following the end of the 2025/26 tax year you need to file for. So, 5 October 2026 for the 2025/26 tax year. Here's why. * HMRC will send you a Unique Taxpayer Reference (UTR) number.
Guard that with your life.
Gather Your Documents: This is arguably the most important step. So organise all relevant financial records for the 2025/26 tax year — 6 April 2025 to 5 April 2026 — which is something that catches a surprising number of people off guard when they first encounter it. in my experience, this includes: * Your UTR number.
P60 — if employed, . P45. if you left a job, . P11D. for employment benefits and expenses, . Bank statements, invoices, receipts for self-employed income and expenses. Records of any other income. Rental income. Foreign income. Dividend statements. Interest certificates. Details of pension contributions. relief at source, . Details of Gift Aid donations. Records of any capital gains or losses. * Information on student loan repayments.
Right, so how do you actually send this stuff in? Most folks just do it online, straight through HMRC's own website. Honestly, it's usually the quickest way. And you know what? A surprising number of people get a bit stumped when they first try it, thinking it'll be more complicated than it is. It's not. What's stopping you from trying that?
Alright, so sorting out your tax return. It's really not as tricky as it once was, honestly. The system even crunches the basic numbers for you now, which is a huge help! You don't have to worry about fiddly calculations. But, are you actually making the most of it? It's pretty straightforward.
So, you know how HMRC makes everything a bit of a faff? Well, first off, you'll absolutely need a Government Gateway account if you don't have one yet – and honestly, if you've ever tried to do this yourself, you'll totally get why that's actually quite useful. Or, hey, your HMRC GOV.UK One Login works just as well. But for businesses, or even just us techy types, there's commercial software. Loads of accounting programmes connect directly to HMRC, letting you file everything straight through. So convenient. But what if you're a bit old school, still like pen and paper? You can still request a paper form, the SA100. Just don't forget, the deadline for that is earlier, 31st October. Don't miss it! And let's be real, you could always just hand it all over to an accountant or tax adviser. They'll just sort it all out and file it for you. Easy. Why wouldn't you, sometimes?
Right, so doing your tax return online. Honestly, it's not the monster it seems, is it? (easier said than done, of course) You just log into your Government Gateway account – and trust me, if you've ever wrestled with a calculator and a pile of receipts, you'll totally get why this is such a lifesaver. Simple. But seriously, who has time for all that paperwork anymore?
First things first, make sure you're picking the correct tax year, which for this one is 2025/26. Easy. Then, the system basically holds your hand, walking you through all the different bits based on where your money comes from, which is something that catches a surprising number of people off guard when they first encounter it. How good is that? It really simplifies things.
Alright, so you're staring at your SA100, yeah? That's your main tax return form. It's basically where you pop all your personal info, plus any income you got from a job – that's the stuff off your P60 or P45, remember? It's pretty straightforward for those bits. But what about other income?
And then, oh boy, you've got to add in any other income sources you've got kicking about, though the practical reality of how this works in practice is rather more complicated than the headline figure might suggest. But honestly, that's just the start of it, isn't it? What a faff!
* SA102. Employment, : For employed income. if not automatically populated, . * SA103. Self-Employment, : For sole traders, reporting income and allowable expenses. * SA105. UK Property, : For rental income and expenses. * SA106 (Foreign): For foreign income. * SA108. Capital Gains, : For reporting capital gains and losses. * Be utterly thorough. Check every single figure twice.
Honestly, when you're doing your tax return online, HMRC's system just sorts out all the sums for you — and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. Pretty handy, eh? Most people are genuinely shocked by that the first time they use it.
You'd think they'd make it harder, wouldn't you? But no, it lays it all out: your total income tax, any National Insurance you're on the hook for if you're self-employed, and even those 'payments on account' you might need to stump up for next year's tax bill.
It's all there.
5. Submit Your Return: * Review all sections one last time. And if you've ever tried to work through the calculations yourself, you'll know exactly what I mean, which is something that catches a surprising number of people off guard when they first encounter it. (a common sticking point for many) * Click 'Submit.' You'll get a confirmation reference. So keep that safe for your records.
Right, so paying your tax bill. It's actually a bit more fiddly than it sounds, isn't it? You've got options, which is good: you can just pay online with your debit card, or do a bank transfer – that's your Faster Payments, CHAPS, or Bacs.
There's also Direct Debit, but honestly, getting that set up and working smoothly can be a bit of a faff, which is something that catches a surprising number of people off guard when they first encounter it. The main thing? Just make sure the money hits HMRC's account by 31 January 2027. Don't miss that deadline! To avoid that interest and those penalties.
HMRC help: Get Custom Help to File Your Tax Return Correctly
Now, here's a bit of good news that's been making waves: HMRC is really stepping up its game with 'HMRC help.' This isn't just a fancy new name for the helpline; it's a proactive, data-driven initiative designed to give you custom help right when you need it, aiming to make your Self Assessment experience smoother and, key, more accurate. It's been gradually rolling out and expanding, particularly for the 2025/26 tax year, and it's all about preventing mistakes before they happen. (and yes, that's as confusing as it sounds)
How to Access and Use HMRC help Services
Right, so how does this actually help you? It's mostly built right into the online Self Assessment system itself. As you're going through your digital tax return, HMRC's system just uses all the stuff it already knows about you – think your PAYE earnings, any bank interest your bank's told them about, and even your old tax returns – to throw up really personalised tips and advice. Pretty neat, eh? Saves a lot of head-scratching. But it's not going to do everything for you, obviously.
* Pre-populated data: For many, sections of your return might already be pre-filled with information HMRC has received from employers, banks, or other third parties. Always check this carefully, but it's a huge time-saver. * Contextual help: If you're entering details in a section related to, say, rental income, HMRC help might flag common errors or give direct links to specific guidance on allowable expenses for landlords. * Targeted messages: HMRC is increasingly sending out personalised emails or messages via your Government Gateway account, reminding you about specific obligations or common traps relevant to your tax profile. Say, if you've before reported foreign income, you might get a reminder about declaring all overseas earnings. * Digital tools: The online service now includes improve calculators and tools that help you figure out things like capital gains or allowable mileage, reducing the chance of manual calculation errors.
Benefits of Using HMRC help for Compliance and Accuracy
So, HMRC help? It's really just about making fewer mistakes. They want to make it simpler for you to get things right the first time around, which is great for everyone, right? It means you won't make those expensive blunders, and they won't have to chase you up for every little thing. Saves hassle all round.
* Reduced errors: By providing real-time guidance and pre-filling data, the system helps you avoid common mistakes that lead to penalties. HMRC's own data suggests that targeted interventions can significantly reduce filing errors, especially for those with more complex tax affairs. * Time-saving: Less time spent hunting for information or correcting errors means a quicker, less stressful filing process. * Improved understanding: The contextual help means you're learning about your specific tax obligations as you go, building your financial literacy. * Proactive support: Instead of waiting for you to make a mistake, HMRC is trying to guide you away from them, which is a welcome shift for many taxpayers.
HMRC help vs. Professional Advice: When to Use Which
So, HMRC giving out help? Yeah, it's a nice thought, a step in the right direction, I guess. (though the reality is often messier) But honestly, it's not a magic bullet, is it? It's definitely not going to replace getting proper advice from someone who actually knows what they're talking about, especially if your tax stuff is a bit of a nightmare. Don't you think it's a bit rich for them to offer 'help' when they make it so complicated in the first place? Get proper advice.
* Use HMRC help for: Straightforward queries, understanding basic requirements, checking pre-filled data, and handling the online portal. It's excellent for ensuring you don't miss obvious sections or make simple calculation errors. * Consider professional advice for: Complex income streams (e.g., multiple businesses, intricate foreign investments), significant capital gains, intricate property portfolios, or if you're unsure about the 'wholly and exclusively' rule for expenses. A qualified accountant or tax advisor can offer custom advice, planned planning, and represent you in dealings with HMRC. They can also help you improve your tax position, which HMRC help, by its nature, can't do.
Ultimately, HMRC help is a powerful tool in your Self Assessment arsenal for 2025/26, designed to help you to file accurately, and that's before you even factor in the additional complications that arise from the interaction with other reliefs and allowances. But knowing its limitations and when to seek expert help is key to truly mastering your tax obligations.
Common Allowable Expenses
Alright, so for us self-employed folks and landlords, getting your head around allowable expenses? Honestly, it's everything. (something HMRC doesn't always make clear) It really is. It's the absolute heart of not handing over more cash to HMRC than you have to, which, let's be real, they'd love you to do. Can you imagine? And it's not always simple figuring out what counts and what doesn't, is it? But knowing this stuff is just so, so important for your bottom line.
It's how you chip away at your tax bill, right? An allowable expense is basically anything you spend 'wholly and exclusively' for your business or property, and honestly, if you've ever tried to figure that out yourself, you'll know the pain. What a headache!
But why's it such a faff?
So, for us self-employed folks, the sole traders, it's pretty straightforward, right? You just tell HMRC what you've earned and what you've spent. Simple. But honestly, sometimes it feels like they go out of their way to make it sound more complicated than it needs to be, which is something that catches a surprising number of people off guard when they first encounter it. Don't you think?
* Office Costs: Stationery. Postage. Printing. Computer bits and bobs. * Travel Costs: Fuel. Public transport fares. Vehicle insurance. Repairs. Servicing. if using a vehicle for business, . You can claim simplified expenses for mileage instead of actual costs. * Clothing: Uniforms. Protective gear. not your everyday wardrobe, obviously, . * Staff Costs: Salaries. National Insurance. Pension contributions for employees. * Premises Costs: Rent. Rates. Utilities. Insurance. for business premises, . If working from home, you can claim a fixed rate or a proportion of household bills. * Advertising and Marketing: Website costs. Online ads. Direct marketing. * Training Courses: Directly related to sharpening skills for your business. not just general education, . * Professional Fees: Accountant. Solicitor. Surveyor fees. * Subscriptions: Trade publications. Professional bodies. * Financial Costs: Bank charges. Interest on business loans. * Insurance: Public liability. Professional indemnity.
For Landlords. UK Property, :
* Maintenance and Repairs: Replacing broken items like a boiler or roof tiles. Not improvements, which are capital expenditure. * Legal and Professional Fees: Estate agent fees. Letting agent fees. Accountant fees. * Insurance: Landlord insurance. * Rent, Rates, Council Tax: If you pay these for the property. * Utilities: Gas. Electricity. Water. if you pay them, . * Interest on Buy-to-Let Mortgages: This isn't fully deductible anymore. Instead, a basic rate tax credit (20%) is given on mortgage interest payments. * Replacement of Domestic Items: For furnished properties, you can claim tax relief for replacing domestic items like beds, sofas, or white goods.
Important Considerations: * Keep detailed records. receipts, invoices, for all expenses. * Don't claim for personal expenses. That's a big no-no. * If an expense has both personal and business use – a mobile phone, say – you must split the cost fairly, which is something that catches a surprising number of people off guard when they first encounter it.
Payment on Account
Right, so you know how you pay your tax? Well, 'Payment on Account' is basically a system where you pay some of your income tax – and your Class 4 National Insurance if you're self-employed – a bit in advance. It's not too tricky.
So, when do you actually have to bother with this whole Self Assessment palaver, eh? Honestly, it's usually only if your tax bill from last year was a grand or more – yeah, £1,000 – even before they took off any of those lovely deductions or allowances. That's a big bill! Don't you just hate how HMRC makes everything so fiddly? But, if it was less than that, you're probably off the hook. Lucky you.
And the other bit? Less than 80% of your tax was already paid through your wages, like with PAYE, though the practical reality of how this works in practice is rather more complicated than the headline figure might suggest. Does that make sense? It's pretty common, actually!
Makes sense, doesn't it?
Right, so these 'Payments on Account' from HMRC? They're basically just them wanting half your tax bill from last year paid upfront. Twice a year, can you believe it? It's a bit of a pain, I know. They literally just take your previous year's tax bill, slice it straight down the middle, and that's your amount for each payment. Simple. And honestly, if you've ever tried to figure out those sums yourself, you'll totally get what I mean about it being a bit much.
* 1st Payment: Due by 31 January during the 2025/26 tax year. * 2nd Payment: Due by 31 July following the end of the 2025/26 tax year.
Your 'balancing payment' – any remaining tax due for the previous year – is also due by 31 January, which is something that catches a surprising number of people off guard when they first encounter it. And if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. Example for 2025/26: If your tax bill for 2024/25 was £3,000. Here's why.
* 31 January 2026: Pay £1,500, 1st Payment on Account for 2025/26. . * 31 July 2026: Pay £1,500, 2nd Payment on Account for 2025/26. . 31 January 2027: Pay any balancing payment for 2025/26. And* your 1st Payment on Account for 2026/27.
You can reduce your Payments on Account if you know your income will be lower this year, and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. But if you reduce them too much, you could face interest charges. A tricky balancing act.
Common Mistakes to Avoid
Even seasoned filers can trip up. So here are some common problems. And how to steer clear of them, which is something that catches a surprising number of people off guard when they first encounter it — and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean.
Missing Deadlines: The most common mistake, which is something that catches a surprising number of people off guard when they first encounter it, and that's before you even factor in the additional complications that arise from the interaction with other reliefs and allowances. And it's easily avoidable. (a detail that trips up more people than you'd think)
Set reminders well in advance.
Not Registering: If you meet the criteria, you simply must register, though the practical reality of how this works in practice is rather more complicated than the headline figure might suggest. HMRC will eventually catch up. And that means penalties.
Right, so tax stuff, eh? It's a bit of a headache sometimes. And honestly, most people just stumble over the same few things — and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean.
What's the biggest culprit? Messy records. Seriously, it's a nightmare when clients don't keep good track of their paperwork. Then there's missing deadlines – that's a classic, isn't it? You forget to file something, or pay on time, and suddenly you're looking at penalties. Oh, and not claiming everything you're entitled to. People often just don't know what they can deduct, so they leave money on the table, which is something that catches a surprising number of people off guard when they first encounter it. Are you guilty of any of these, then? It happens.
Seriously, if you don't keep all your receipts, invoices, and bank statements neat, you're probably missing out on claiming things you could, and that's before you even factor in the additional complications that arise from the interaction with other reliefs and allowances. Or worse, getting your income wrong. Big no-no.
Then there's trying to claim stuff that's not actually for the business – like that new pair of shoes you bought, even if you wore them to a meeting. HMRC calls it 'wholly and exclusively' for a reason, right? Personal stuff just doesn't count. And oh, income! You've got to declare everything. Untaxed interest, dividends, any foreign money you've got coming in. It all counts. Trust me, if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. Everything. Another thing people forget is Payments on Account. They're part of your tax bill, not some random extra. You've got to plan for them financially. And please, for the love of all that's good, always double-check everything before you hit that 'submit' button. Just look it over. But honestly, if you're ever scratching your head, just ask! HMRC, an accountant, a tax advisor – they're there for a reason. Why guess when you don't have to?
Honestly, the biggest blunder people make with their taxes? Just putting it off. Seriously. It's like, why do we do that to ourselves? You know it's coming, but we still leave it till the last minute, don't we? So silly.
You leave it until the last minute, and suddenly you're staring at a screen, probably on January 30th, trying to figure out some obscure calculation, and that's when mistakes happen, or you just miss the deadline entirely. And if you've ever tried to do your own sums, you know what a nightmare that can be, right? It's way more fiddly than the headline figures ever let on. Good tax planning, my friend, starts way, way before January 31st. Why do people do this to themselves?
Practical Example: Freelancer's Self Assessment for 2025/26
So, imagine Jane, she's a freelance graphic designer. That's a classic one, isn't it? People often get totally thrown by how tax works for freelancers when they first start out – and honestly, if you've ever tried to crunch those numbers yourself, you'll know exactly what I mean.
It's a bit of a minefield. But for her, we're looking at her income for the 2025/26 tax year, though the practical reality of how this works in practice is rather more complicated than the headline figure might suggest. Got it?
* Freelance Design Work: £35,000 * Bank Interest (untaxed): £200 * Dividends from UK shares: £800
Allowable Expenses for 2025/26:
* New Laptop: £1,200, capital allowance claimed for 100%. * Software Subscriptions: £400 * Professional Indemnity Insurance: £300 * Home Office, simplified expenses. : £312, £26/month x 12. * Website Hosting & Domain: £150 * Accountant Fees: £250 * Travel to client meetings: £100
Other Relevant Info:
* Jane made personal pension contributions, relief at source. : £2,000 * Jane's 2024/25 tax bill was £3,200. So she has Payments on Account.
Calculation, Simplified. :
So, imagine you're running your own little business, right? You've pulled in a tidy £35,000. Not bad!
But then you've got to subtract all those bits and bobs you spent to actually make that money, which is something that catches a surprising number of people off guard when they first encounter it. Things like £1,200, then another £400, £300, £312, £150, £250, and a final £100. Add all that up, and your total allowable expenses come to £2,712. Not quite.
Simple deductions. So, after those basic expenses, your actual taxable business profit is £32,288 — and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. Makes sense?
Alright, so let's break down your tax situation for 2025/26, which is something that catches a surprising number of people off guard when they first encounter it. Basically, your business profit was £32,288.
Good stuff.
Right, so you know that £200 in bank interest and the £800 in dividends you were a bit worried about? Guess what! We don't even need to worry about those for tax.
Honestly, it's brilliant. You just don't pay tax on them at all, which is pretty sweet, right? And that's even before we get into how it simplifies things by not having to worry about them messing with your other tax breaks and allowances. They just vanish. Simple as that.
Honestly, it's pretty straightforward, for once. Both of those just slot right into your personal savings allowance and your dividend allowance. Poof! Tax-free. How good is that? No tax to pay on them. Don't you just love it when HMRC makes something simple, even if it's just for a moment?
How cool is that? After we've factored in your pension contributions, your 'adjusted net income' is still £32,288. Then, we just knock off your Personal Allowance – that's £12,570 for that year, by the way. That leaves us with £19,718 that actually gets taxed. And because that whole amount is within the 20% basic rate band, it's taxed at 20%, bringing your total tax bill to £3,943.60. But you've already paid £3,200 in 'payments on account' based on what you earned last year, haven't you? So, you're only going to owe an extra £743.60. Not too shabby, right? Just a little top-up. Oh, and looking ahead to 2026/27, you'll need to make two payments on account of £1,971.80 each – one by 31 January 2027 and the other by 31 July 2027. Just a heads-up for your calendar!
Jane should file her return as early as possible, and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. So she'll know exactly what she owes. And can plan her cash flow so.
Key Takeaways
* The Self Assessment deadline for 2025/26 online returns is 31 January 2027. Paper returns must be filed by 31 October 2026. * You must register for Self Assessment if you're self-employed. Or a landlord. Or have untaxed income over £1,000. Or meet other qualifying criteria. * Keep records for at least 5 years after the 31 January submission deadline. HMRC can open enquiries within this period. * Claim all allowable expenses: office costs, travel, professional subscriptions. And use simplified expenses for home office. £26/month for 101+ hours, . * Payments on Account are advance payments towards next year's tax bill. Each instalment is 50% of the previous year's liability. * Use HMRC help within the online portal for custom guidance and pre-filled information, helping to improve accuracy and reduce errors. * File early to know your liability. Spread payments. And avoid the January rush when HMRC helplines are busiest. * Consider using Making Tax Digital compatible software. It will simplify your record-keeping. And prepare you for the MTD transition.
Frequently Asked Questions
When do I need to register for Self Assessment?
You must register by 5 October following the end of the 2025/26 tax year in which you first need to file — and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. Say, if you became self-employed during the 2025/26 tax year. 6 April 2025 to 5 April 2026, , you must register by 5 October 2026. Late registration can result in penalties.
What happens if I miss the 31 January deadline?
So, get this, you'll automatically get hit with a £100 penalty. One hundred quid! Even if you don't actually owe any tax, which, let's be honest, if you've ever tried to figure out HMRC's sums yourself, you'll totally get how maddening that's.
So, you might have already paid everything you owe, which honestly, catches a lot of people by surprise when they first see it, though the practical reality of how this works in practice is rather more complicated than the headline figure might suggest. It's a common thing. Still, that £100? You've probably already settled up. Does that make sense?
Doesn't that just boil your blood?
After 3 months, additional daily penalties of £10 per day. up to 90 days, apply. After 6 months, a further penalty of 5% of the tax due or £300, whichever is greater, is charged, which is something that catches a surprising number of people off guard when they first encounter it.
After 12 months, another 5% or £300 penalty applies. Interest also accrues on any unpaid tax from the due date — and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. A real headache.
Can I claim working from home expenses?
Yes. If you work from home for your self-employment, you can claim a proportion of household costs, which is something that catches a surprising number of people off guard when they first encounter it. Heating.
So, for all that electricity and broadband you're using working from home, what's the easiest way to deal with it for tax? Honestly, HMRC's 'simplified expenses' flat rate is your best bet. It's just simpler. Why make it harder than it needs to be, eh?
So, if you're working from home for, say, 25 to 50 hours a month, you can claim a flat £10 a month, and that's before you even factor in the additional complications that arise from the interaction with other reliefs and allowances. Pretty neat, right? It's that simple.
What about if you work more? It jumps to £18 a month for 51-100 hours. Or, if you're really putting in the time, it's £26 a month for 101+ hours. And if you've ever tried to work through the calculations yourself, you'll know exactly what I mean, though the practical reality of how this works in practice is rather more complicated than the headline figure might suggest.
Easy, right? Your other option is to actually work out the exact bit of those costs that are purely for your business, which is something that catches a surprising number of people off guard when they first encounter it. And if you've ever tried to work through the calculations yourself, you'll know exactly what I mean.
Bit more faff, that.
Do I need to include my PAYE income on my Self Assessment return?
Yes. Even though tax has already been deducted from your PAYE employment income, you must declare it on your Self Assessment return, and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean. This ensures your total income is assessed correctly. Especially if you've multiple income sources. These might push you into a higher tax band.
What records do I need to keep?
Honestly, you wouldn't believe how many people get tripped up by this when they first start out, but you absolutely have to keep records of every single penny you earn and spend. Every. Single.
One. It's not just about the big stuff either, like your main invoices; we're talking every little receipt too, which is something that catches a surprising number of people off guard when they first encounter it. Who keeps all those? It's a pain, I know, but HMRC expects it, so don't get caught out.
Honestly, it's a bit of a pain, isn't it? You really do have to hang onto every bank statement, all your mileage logs, and basically any other paperwork that proves what you've declared on your tax return. Why can't they just make it easier for us? Keep everything. And I mean everything, because HMRC can ask for proof up to six years after you've filed, and if you don't have it, you're in trouble.
So, for self-employment, what do you need to keep? Basically, sales records, buy invoices, and all your expense receipts. Easy, right? Well, you've got to hang onto them for at least 5 years after the 31 January submission deadline. and if you've ever tried to work through the calculations yourself, you'll know exactly what I mean.
Yeah, it's never as straightforward as it seems, is it? Always a few more hoops to jump through than you'd expect. Don't you find that with most things, though?
Can I amend my tax return after filing?
Yes, you absolutely can amend your Self Assessment tax return after you've filed it. You've up to 12 months from the filing deadline to make changes. So, for your 2025/26 return, which is due by 31 January 2027, you'd have until 31 January 2028 to submit any amendments, which is something that catches a surprising number of people off guard when they first encounter it. Not quite.
You can do this directly through your HMRC online account. If you've used commercial software, you can usually amend it through that too. If the amendment changes your tax bill, HMRC will issue a new calculation. Big difference. If you're outside this 12-month window, you'll need to write to HMRC with details of the error and why you couldn't correct it earlier, and that's before you even factor in the additional complications that arise from the interaction with other reliefs and allowances.
So, with the tax year drawing to a close, isn't it worth taking a moment to make sure everything's shipshape, rather than crossing your fingers and hoping for the best? A quick check now could save you a real faff later, and who wouldn't want that?