Accounting deadlines every self-employed person should know

Running your own business means juggling a lot of plates, and your tax deadlines are one thing you can’t afford to drop.

If you miss one, it’s usually HMRC who benefits, not you.

This guide outlines the key dates that sole traders and self-employed individuals should be aware of. We’ve also linked to some useful tools and resources to help you stay organised.

31st January – File and pay your Self Assessment

This is the big one. You need to submit your Self Assessment tax return and pay your income tax by midnight on 31st January each year.

The return covers the previous tax year (which runs from 6 April to 5 April), so for the 2024/25 tax year, the deadline is 31st January 2026.

If you miss it, you’ll get a £100 late filing penalty straight away — even if you don’t owe any tax. And interest starts building up daily if you don’t pay on time.

Here’s how Self Assessment works, including what info you’ll need to include.

31st July – Second payment on account (if it applies)

If your last tax bill was over £1,000, and you don’t have much tax deducted at source, HMRC will usually ask you to make two “payments on account” toward your next bill.

The first one’s due on 31st January. The second one lands on 31st July.

It catches a lot of people out, especially in their first few years of trading. If cash flow is tight, you can ask HMRC to reduce it — but be careful, or you could end up underpaying.

Check your payment schedule on GOV.UK.

5th October – Register for Self Assessment (first-time filers only)

If this is your first year going self-employed, you need to tell HMRC by 5th October after the tax year you started in.

For example, if you started trading in May 2025, you need to register by 5th October 2026. If you miss it, you might still be expected to file — but without a prompt or UTR code, it gets messy.

Here’s how to register if you haven’t done it before.

6th April – New tax year begins

The UK tax year starts on 6th April. This is a good time to draw a line under last year’s accounts and get your books sorted early — especially if you want to avoid the January rush later on.

It’s also when most allowances reset, including:

• Your personal allowance
• Pension contributions
• Annual investment and trading allowances

Want to tidy things up? Start by reviewing your records and getting your bookkeeping in order.

Quarterly or monthly – VAT deadlines

If you’re VAT-registered, you’ll have extra deadlines to meet. Most small businesses file VAT returns quarterly, with the return and payment due one month and 7 days after the end of each VAT period.

So if your period ends on 31st March, you’ve got until 7th May to file and pay.

And under Making Tax Digital (MTD), you’ll need to use compatible software to file. No more typing numbers into the old online form.

Here’s what to avoid when filing VAT.

Real-time and monthly – Payroll and CIS deadlines

If you pay staff (or yourself via PAYE) or deal with subcontractors under the Construction Industry Scheme, there are even more dates to watch.

• RTI (Real Time Information) submissions are due on or before each pay date
• CIS returns are due by the 19th of each month for the previous month’s payments

Need to set up payroll or CIS reporting? It’s not as bad as it sounds — and you don’t have to do it alone.

What about MTD for Income Tax?

This is still in the pipeline — but from April 2026, self-employed people earning over £50,000 will need to follow Making Tax Digital rules for income tax too.

That means submitting quarterly updates, not just one big Self Assessment return in January. If you’re over the threshold, you’ll need to start using compliant software in good time.

More on MTD here.

Do you need to keep records after filing?

Yes — HMRC expects you to keep your records for at least 5 years after the 31st January filing deadline. That includes receipts, mileage logs, invoices and anything else that supports your return.

If they ask questions later, and you don’t have proof, you’re on the back foot.

Here’s what to keep and how long.

Tips to stay on top of everything

• Put every key date in your calendar now — don’t wait for reminders
• Use accounting software that flags deadlines and alerts you
• Work with an accountant who chases you up (not the other way round)
• Don’t leave it until January — it never ends well

If you want to go down the software route, we’ve reviewed a few options here.

Summary

There are a lot of moving parts when you’re self-employed, and deadlines come around faster than you think. Miss one, and you’re looking at penalties, interest, and extra hassle.

So build good habits early. Stay on top of the admin. And if it all feels too much, it might be time to bring in an accountant.