Startups To Help You With Your Self Assessment Tax Return

For sole traders operating in the UK, the 31st is an important date that you probably want to keep track of.

Every year, HMRC has a deadline by which tax returns need to be completed. For the tax year 24/25, the main self assessment deadline is 31 January 2026 for filing your tax bill online and paying any taxes.

For some, this deadline is something they’ve been working towards all year. For others, mid-January means panic stations.

What Happens If You Don’t Do Your Tax Return By January 31st?

If you don’t file your UK self assessment tax return by January 31st you’ll probably start seeing penalties roll in from HMRC.

These include:

• An initial £100 penalty
• After 3 months, additional daily penalties of £10 per day, up to a maximum of £900
• After 6 months, a further penalty of 5% of the tax due or £300, whichever is greater
• After 12 months, another 5% or £300 charge, whichever is greater

But it’s not just filing that can land you in hot water. If you pay your tax late you’ll get penalties of 5% of the tax unpaid at:

• 30 days
• 6 months
• 12 months

On top of this, you’ll also be charged interest on the amount owed.

Who Needs To File A Self Assessment Tax Return?

If you’re not sure whether you need to fill in a self assessment tax return, you do if the following applies to you:

• You are self employed as a sole trader and earned more than £1000 (pre-expenses)
• You were a partner in a business
• You sold shares or another asset that you need to pay Capital Gains Tax on
• you had to pay the High Income Child Benefit Charge and do not pay it through PAYE

You may also need to send a tax return if you have any untaxed income, like:

• money from renting out a property
• tips and commissions
• income from savings, investments and dividends
• foreign income

If you want to be triple sure, you can check through HMRC here.

What Startups Exist To Help?

But don’t panic. If you find yourself needing to file the return in the next week and can’t get hold of an accountant, there are actually a few startups that exist to help.

Here are some of the ones we recommend.

Pie Tax

Pie is the UK’s first self-assessment app, founded to help make taxes simpler and easier to file when needed.

Through the app, users can record transactions and expenses, allowing them to file their tax returns easily and quickly. If needed, Pie also has experts on hand to help with any tricky questions if needed, making it easy for anyone approaching the filing deadline.

Taxfix

Taxfix is an app that allows people to file their taxes from anywhere. Through Tax Fix, users can get their self assessment filed by a real human accountant from just £119.

This system means that their customers not only get support through the process, but have a real UK-accredited accountant to help them work through the details.

Anna Money

Anna Money is a business accounting software that actually lets you file your self assessment for free. According to Anna Money, you don’t need an expensive, complicated accounting software. Instead, they will file your initial self assessment for free and then charge £15 per month thereafter to help you stay on top of the numbers.

GoSimpleTax

GoSimpleTax is an HMRC-recognised online tax software for anyone that needs to file a self-assessment. With over 20,000 customers in 30 countries and 125,000 tax returns submitted to date, it’s a great option for anyone approaching the deadline fast.

Sleek

Sleek is an accounting startup that helps people file their self-assessments and transition easily to digital accounting.

With no hidden fees and quick turnaround, it’s a great option for anyone on an HMRC deadline. Not just a software, Sleek also has a team of experts so you always know your accounts are in good hands.