How To File Your First Self Assessment

Filing your first Self Assessment comes down to four things: registering with HMRC on time, keeping decent records through the year, filing before 31 January, and paying what you owe. None of it is complicated on its own. It just adds up if you leave everything until the deadline.

Key Takeaways

• Register for Self Assessment with HMRC by 5 October after the end of the tax year you need to file for.
• Keep records of self-employed income, employment income, pension contributions, and anything else relevant through the year, not just before filing.
• The filing and payment deadline is 31 January following the end of the tax year.
• If your gross income from self-employment or property is over £50,000, you're now required to use Making Tax Digital instead of traditional Self Assessment.
• You can't pay what you owe using a personal credit card, so check your payment method works before the deadline.

When Do I Need to Register for Self Assessment?

You need to register with HMRC by 5 October after the end of the tax year you're filing for. For example, if you need to file for the tax year ending 5 April 2026, you should register by 5 October 2026.

Miss that date and you can face a penalty, even if you file and pay on time afterward. You can register online, by post, or by phone, and you'll need your National Insurance number along with your personal and business details. Once registered, HMRC issues you a Unique Taxpayer Reference (UTR), which you then use to set up access to file online.

What Records Do I Actually Need to Keep?

Good records make filing straightforward. Bad or missing records are where most first-time filers run into trouble. Keep track of things as you go, rather than trying to reconstruct a year's worth of numbers in January.

Depending on your situation, you'll typically need:

• Self-employed income, including invoices and business expenses
• Employment income, such as a P60, a P45 if you left a job during the tax year, and a P11D if relevant
• Pension contributions and pension income
• Any payments on account you've already made
• Capital gains, if applicable

Digital accounting software makes this considerably easier to manage than a folder of receipts, and it's becoming a requirement rather than just a convenience for some filers, covered below.

How Do I Actually Fill In and File the Return?

File as early in the tax year as you can, once you've registered and have your UTR and login details. Filing early doesn't change what you owe, but it gives you breathing room if something's missing or unclear.

Once you're logged into HMRC's online system, the process itself is straightforward if your records are in order: you enter your income and expenses, and the system calculates what you owe.

What's Changed: Making Tax Digital for Income Tax

If your gross income from self-employment or property is over £50,000, traditional Self Assessment has already been replaced for you. Since April 2026, Making Tax Digital for Income Tax requires digital record-keeping and quarterly updates to HMRC instead of a single annual return.

This threshold is dropping over time: down to £30,000 from April 2027, and £20,000 from April 2028. If you're close to £50,000 now, it's worth checking your position before assuming the old system still applies to you next year. Our guide to Making Tax Digital for sole traders covers the rules, thresholds, and deadlines in full.

How Do I Pay What I Owe?

Once you've submitted your return, HMRC tells you what you owe, and you can pay by Direct Debit or bank transfer, among other options listed on GOV.UK. You can't pay using a personal credit card, so it's worth confirming your payment method works well before the 31 January deadline.

Should I Use an Accountant?

An accountant can organise your records and handle the filing itself, and some will file on your behalf entirely. If you're filing for the first time and feel unsure about any part of the process, this is often the fastest way to get it right without second-guessing yourself.

If you'd rather not use an accountant, digital accounting software can still keep your records organised and make the filing itself far less stressful, particularly once Making Tax Digital applies to your income level.

FAQs

When do I need to register for Self Assessment?

By 5 October after the end of the tax year you're filing for. Missing this deadline can lead to a penalty even if you file on time afterward.

What's the deadline to file and pay my Self Assessment?

31 January following the end of the tax year, for both filing your return and paying what you owe.

Do I still need to do traditional Self Assessment if I'm self-employed?

Only if your gross income from self-employment or property is under £50,000. Above that threshold, Making Tax Digital for Income Tax now applies instead.

Can I pay my Self Assessment bill with a credit card?

No. Personal credit cards aren't accepted. You can pay by Direct Debit, bank transfer, or another method listed on GOV.UK.

What happens if I don't keep proper records through the year?

You risk an inaccurate return, a stressful filing process, and potentially an incorrect tax bill. Keeping records as you go is far easier than reconstructing them in January.

Can an accountant file my Self Assessment for me?

Yes, many accountants can prepare and file it on your behalf, which can be worth it if you're filing for the first time or your income situation is more complex.

This article is for general information only and does not constitute tax or legal advice. Self Assessment rules, thresholds, and deadlines can change, so it's worth checking current guidance on GOV.UK or speaking to a qualified accountant before filing.