Self Assessment Deadlines Every Freelancer Should Know

 If you’re new to freelancing, side hustling, or running your own small business in the UK, understanding your tax responsibilities can feel overwhelming at first. One of the most important things to stay on top of is the Self Assessment process—and more importantly, the deadlines that come with it.

Missing these dates could mean unnecessary fines, stress, and HMRC letters you really don’t want. Let’s break it all down clearly so you know exactly what to do and when.

Who Has to Submit a Self Assessment Tax Return?

If you're self-employed, even part-time, you probably need to submit a Self Assessment tax return. This includes:

• Freelancers (yes, even if it’s just a side gig)
• Sole traders
• People earning income outside of PAYE (like rental income or investments)
• Those who have untaxed income over £1,000

Not sure how to get started with your self assessment tax return? Check out our full step-by-step guide to registering for Self Assessment.

Key Self Assessment Deadlines in the UK

Here are the Self Assessment deadlines UK freelancers and sole traders need to mark in their calendar each year.

5 October – Register for Self Assessment

If you started earning untaxed income in the last tax year (which ends on 5 April), you must complete your registration with HMRC by 5 October.

Example: If you started freelancing in May 2024, you must register by 5 October 2025.

31 October – Paper Tax Return Deadline

If you’re sending your tax return by post (not many do these days), it needs to reach HMRC by 31 October. It’s old school—but still an option.

31 January – Online Tax Return Deadline & Payment Due

This is the big one.

• Make sure to file your online tax return before midnight on 31 January.
• Pay any tax you owe by the same date

You can also make a payment on account (essentially, paying half your estimated tax for the next year) if HMRC requires it.

31 July – Final day for second payment on account, if applicable.

If payments on account are required, the second instalment must be paid by 31 July. This is only for those with a larger tax bill and it helps you stay ahead for the next year.

What Happens If You Miss a Deadline?

Missing a Self Assessment deadline can result in penalties that quickly add up. Here’s what will happen if you miss the deadline:

• Late registration could lead to a ‘failure to notify’ penalty
• Missed return deadline: £100 fine immediately, plus more if it’s later
• Late payment: Interest starts building right away

Staying ahead of deadlines is key. Setting calendar reminders can help you avoid unnecessary stress and save you money

Quick Tips to Stay on Track

1. Use apps or spreadsheets to track income and expenses regularly
2. Set reminders for deadlines (don’t rely on memory)
3. Submit your return early—you don’t have to wait until January!
4. If it feels like too much, a good accountant can handle it for you.

Staying organised and on top of things will help you avoid stress and keep everything running smoothly.

Frequently Asked Questions About Self Assessment

Q:When do I need to register for Self Assessment as a freelancer?

A: You must register with HMRC by 5 October following the tax year in which you started earning untaxed income.

Q: Do I need to pay tax if I earn under £1,000?

A: If your total untaxed income is under £1,000, you may not need to file a Self Assessment tax return. However, if you have other untaxed income or capital gains, you might still need to register and file.

Q: Can I file my self assessment tax return online?

A: Yes, HMRC encourages online submissions. You can file your Self Assessment tax return through the HMRC website or using approved software.

Q: Do I need to file a Self Assessment tax return if I have a full-time job?

A:If you have additional untaxed income, such as freelance earnings, rental income, or investments, you may need to file a Self Assessment tax return.

Q: Can I pay my tax bill using my PAYE tax code?

A: If you owe less than £3,000 and are employed or receive a pension, you may be able to have your tax bill collected through your PAYE tax code. You must opt for this by 30 December.

Final Thoughts

Staying on top of your self assessment deadlines is one of the simplest ways to avoid stress, fines, and last-minute panic. Whether you're submitting your first return or you’ve been freelancing for a while, marking these key dates in your calendar can make a big difference. Plan ahead, keep your records tidy, and give yourself plenty of time before deadlines hit. Your future self will thank you. Need help understanding what to do next? Check out our Self Assessment guide for step-by-step support