About SideTax
SideTax is a free UK side hustle tax calculator. We built it because HMRC's new platform reporting rules (effective January 2024) are now generating millions of confused Google searches a year, and the existing answers are either tax-firm content marketing trying to upsell you to a £200 Self Assessment service, or HMRC's own pages, which are written for accountants.
What we do
We give you a straight, plain-English answer to "how much tax do I owe HMRC on this side income?" using the actual rules, trading allowance, tax bands, NI thresholds, the lot. No upsell. No newsletter spam. No "speak to an adviser" gating. Just a calculator and a set of platform-specific guides.
What we don't do
We're not accountants. We don't file your Self Assessment. We don't give regulated tax advice. We're not authorised by the FCA. The calculator and guides are educational tools, and for complex situations you should engage a qualified accountant or chartered tax adviser.
How we make money
SideTax is currently free with no ads. If we eventually add a paid record-keeping tracker (£4.99/month) or affiliate links to bookkeeping software, we'll disclose it clearly. We won't sell your data. We don't track you across the web.
Accuracy
The calculator uses HMRC's published rates and rules for the 2025/26 tax year (England, Wales, Northern Ireland). It does not currently model:
- Scottish income tax bands (different rates)
- Capital gains tax
- Marriage allowance transfers
- Blind person's allowance
- Student loan deductions
- High Income Child Benefit Charge (HICBC)
- Pension contribution tax relief
- Gift Aid
- Foreign tax credits
- VAT registration nuance
If your situation involves any of the above, treat the calculator's output as a rough estimate and verify with an accountant.
Found a mistake?
We genuinely want to know. Tax rules change every year and we'd rather fix an error fast than have it sit in our content. Email feedback to hello@sidetax.co.uk.