When Should I Submit My 2025/26 Self Assessment Tax Return?

You don’t have to wait for the January deadline, and can submit your Self Assessment return as soon as the tax year it covers has ended. In this article we explain the benefits of getting your tax return in sooner, and what you can do to prepare.

How early can I submit my 2025/26 Self Assessment tax return?

A Self Assessment return for a particular year can be submitted from the day after that tax year ends. For example:

• The end of the 2025/26 tax year is 5th April 2026
• You can submit your Self Assessment tax return for the 2025/26 tax year from 6th April 2026 onwards

What if this is my first tax return?

You’ll need to register for Self Assessment before sending a return, so it’s well worth getting everything ready in plenty of time. The registration process isn’t instant, and you’ll need to wait a few days for your authorisation codes to arrive in the post after completing the online form.

The deadline to register for Self Assessment is 5th October in the second tax year, but you can do this much sooner.

Is it better to submit my tax return early?

Completing and submitting your Self Assessment tax return early has several advantages over waiting to do it later. We’ll go over each point in more detail below, but it generally means tax refunds are available sooner, and you have more time to deal with any issues logging in to your Self Assessment online account!

You’re more likely to receive your tax refund sooner

If you’re likely to receive a tax refund (which is often the case for CIS subcontractors in particular), then submitting your tax return sooner means getting that money back faster, too.

Claim back all your allowable expenses

Making your submission earlier gives you more time to review everything properly and reduce the risk of mistakes. It also gives you a chance to claim for all those allowable expenses to reduce your tax bill, and more time to chat to your accountant, bookkeeper, or anyone else who can help you submit your tax return. Watch our video below for our top tax-saving tips.

Give yourself more time to prepare for Self Assessment

You’ll know exactly what you owe, and give yourself more time to pay it over a longer period – which helps with planning your cash flow! Tax returns can be stressful, and paying them can be even worse. Getting your Self Assessment in as soon as possible can help alleviate some of the worrying, and help you prepare – especially if your tax bill is more than £1,000 and you need to make Payments on Account.

If I submit my Self Assessment earlier, do I have to pay straight away?

The date you submit your Self Assessment doesn’t affect the payment deadline, so filing your tax return earlier in the year doesn’t mean you need to pay your bill earlier, too. Unless of course, you want to pay your tax bill early.

Filing earlier simply gives you more time to budget for your tax bill. Which is definitely less hassle than being fined by HMRC for late payment. We explain how tax rates and thresholds work in more detail in a separate article.

Do I still need to send my 2025/26 Self Assessment if I start using MTD Income Tax in April 2026?

Yes, you’ll still need to submit a Self Assessment tax return in the normal way before 31st January 2027 to report your income and expenses for the 2025/26 tax year – even if you start using Making Tax Digital (MTD) Income Tax in April 2026. The MTD system only covers the 2026/27 tax year onwards so you must send a Self Assessment for 2025/26 to cover the period before MTD started.

What are the Self Assessment deadlines for my 2025/26 tax return?

There are slightly different deadlines for submitting your tax return depending on how you send it. It’s important to submit your return and pay any money you owe before the deadline in order to avoid penalties.

Can I make changes to my tax return after I submit it?

Yes, but the process for this depends on whether or not the deadline has passed. We explain this in more detail in our article about making amendments to your tax return.

Talk to us about how our online accounting services can help you with your Self Assessment. Call 020 3355 4047 to chat to the team, and get an instant online quote.