Self Assessment app

A Self Assessment app for side hustlers

Hamster is a Self Assessment app for side hustlers that keeps your earnings, costs and mileage in order through the year, so the figures for your tax return are ready before the deadline. No shoebox of receipts and no piecing the year together in January.

Android app on Google Play

Download free

Built for UK sole traders and side hustlers (HMRC rules)

Hamster’s History screen with two logged entries, £1,000 from driving and delivery on Uber and £1,000 from selling goods on Vinted, and filters by category and date.

Who it’s for

Side hustlers in the UK who file their own Self Assessment return as a sole trader, or hand their figures to an accountant. That includes first-timers who have just gone over the £1,000 trading allowance, and anyone who finds out in January that they can’t remember what they earned in May.

It isn’t built for limited companies or partnerships. Estimates use the rates for England, Wales and Northern Ireland. Scottish Income Tax bands and student loan repayments aren’t included yet.

What Hamster does

You log your earnings, costs and business miles as they happen. Hamster totals them by tax year, estimates your Income Tax and National Insurance, and, with Premium, exports the figures for your return. It also reminds you four weeks, one week and one day before the 31 January deadline, for free. It doesn’t file the return, connect to your bank or track you by GPS.

The features that matter

Free
A full year of records
Every sale, shift, cost and business trip in one place, filterable by category and date, ready when you sit down to file.
Free
Allowance or expenses, worked out
Hamster uses the £1,000 trading allowance until your logged costs beat it, then switches to your actual costs, and estimates the bill.
Premium
Figures by SA103S box
Export a PDF for the tax year with turnover, expenses and net profit labelled by SA103S box. Copy them into your online return or send it to your accountant.
Premium
Receipts kept with each cost
Attach a photo to any expense, so the evidence is there if HMRC ever asks.

Pricing

Hamster (free): Log earnings, costs and mileage, see your tax and National Insurance estimate, and track what you’ve set aside. Free to download and free to use.
Hamster Premium: £4.99 a month or £47.99 a year, billed through Google Play. Adds CSV import, receipt photos, the accountant PDF and threshold alerts. Cancel any time in Google Play. Free trial available on Google Play for eligible accounts.

Questions

Does Hamster file my Self Assessment return?

No. Hamster gets your figures ready. You file the return yourself on HMRC’s website, or pass the figures to an accountant. With Premium you can export a PDF with the figures labelled by SA103S box.

When is the Self Assessment deadline?

For the 2025–26 tax year (6 April 2025 to 5 April 2026), you must file your online return and pay what you owe by 11:59pm on 31 January 2027.

Do I need to register for Self Assessment first?

If your trading income was more than £1,000 in a tax year, you need to register for Self Assessment by 5 October after that tax year ends. Hamster doesn’t register you. You do that on GOV.UK.

Which pages of the tax return does the PDF match?

The full tax-year PDF labels your figures with the box numbers from the SA103S self-employment (short) pages: turnover, expenses, the trading allowance and net profit. It’s a Hamster Premium feature.

Our guides cover the Self Assessment deadline, how to fill in the SA103S self-employment pages box by box, and whether you need to register as self-employed for a side hustle. For tracking all year round, see Hamster as a side hustle tax app.

Get Hamster

Android app, out now on Google Play. Estimates are a guide, not tax advice. How we check our numbers.