I'm the developer, so this is self-promo, but I think it's useful for anyone earning on the side in the UK.

Hamster is an Android app that tracks your side hustle earnings and costs (driving, Vinted/eBay, freelance, Etsy, etc.), tells you roughly what to set aside for tax, and warns you as you get near the £1,000 trading allowance. It also handles mileage at the current HMRC rates and gives you the figures you need for Self Assessment before the 31 January deadline.

It's free to use for the basics. There's a Premium tier (14-day free trial, then £4.99/month or £29.99/year) for extras like profit per mile and per hour, CSV import and an accountant-ready PDF.

It's only on Android for now, and it's new, so I'd really like to hear what's missing or confusing.…