When Do I Need to Submit My Self Assessment Tax Return?

There’s always lots to do and plan when you’re running a business, but taking care of your tax return shouldn’t be near the end of the list. That’s right. We’re saying it. The Self Assessment deadline is never more than 12 months away, so getting your finance records ready will help. We’ll explain how to prepare, and how soon you can submit your next tax return.

When is the Self Assessment tax return deadline?

The deadline for filing Self Assessment and paying what you owe is 31st January.

For example

If you need to submit a tax return to report income earned in the 2025/26 tax year (6th April 2025 – 5th April 2026) the submission deadline is 31st January 2027.

We 100% recommend not waiting until the day to file. Anything can go wrong and thousands of other people are trying to do the same. The best time to file your Self Assessment tax return is before the New Year. It’s best to get it out of the way as soon as possible. Plus, if you’re due a tax rebate you’ll get it sooner!

Who needs to submit a Self Assessment tax return?

Unsure whether you need to submit Self Assessment? You will need to submit a Self Assessment tax return if you earn more than £1,000 of untaxed miscellaneous income (such as from self-employment or property) during the tax year.

For example, if you received £800 from self-employment as well as your normal wages, you don’t have to worry. If you made £2,000 on top of employment income, you will need to file a tax return.

Preparing to complete your Self Assessment tax return

There’s no need to join everyone in a scramble around, so there are lots of things you can do to prepare your submission.

Get all your documents together

It’s a huge help when you have all your documents and accounting information in one place. Items such as transactions, expenses, VAT details and PAYE documents can easily get misplaced if they’re all kept in different places.

The Self Assessment form asks for lots of information about your income, so make sure you have all the details ready.

Claiming expenses

If you want to reduce your tax bill (who doesn’t?) then you can claim expenses which relate to your business. If you’ve spent any money on running the business, this is an expense. For example, stationery, software, equipment, accounting help and hiring costs – they’re all expenses you can claim to reduce your tax bill.

Trading Allowance or expenses?

If your business expenses total less than £1,000 in the year, you might be better off claiming for the Trading Allowance instead. This is a tax-free allowance of £1,000 which any self-employed person can claim on top of the personal allowance. Just remember that you can only claim the allowance or your expenses - not both. Choose the one which gives you the biggest reduction in your tax bill.

Prepare payment

Hopefully you’ve been squirrelling money away from every payment so you have something set aside to pay your tax bill before the 31st January deadline.

If you’ve had to use it to replace your boiler or fix the weird noise on your car, then you might need to talk to HMRC about arranging a Time to Pay agreement instead.

Submitting your tax return early doesn't change the payment deadline.

What happens if I miss the Self Assessment deadline?

The world won’t end but you will be out of pocket. Late tax returns incur an automatic £100 penalty. If you act quickly, you can reduce the fines but if you leave it for three months, you’ll be charged £900. If you’re a whole year late, expect to be hit with an additional 15% penalty.

If you have a legitimate excuse for missing the Self Assessment deadline or not paying the full bill, get in touch with HMRC as soon as possible. They may approve your case so that you don’t have to pay penalties, and they will come to an agreement with you to help you pay what you owe.

Learn more about using Pandle to make business accounting easier. Create an account today and decide what to do with all the extra time you get back.

Elizabeth Hughes

A content writer specialising in business, finance, software, and beyond. I'm a wordsmith with a penchant for puns and making complex subjects accessible.

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