"Gross" means total sales income before any costs — the trading allowance and filing threshold are both based on this figure, not your profit.
This is a fast estimate, not a filed return. It doesn't account for Payments on Account (advance payments HMRC often requires once you're in Self Assessment), Class 2 National Insurance (now voluntary, but worth paying if you want the year to count toward your state pension), or income from other sources like savings interest or dividends. Always confirm your actual position with HMRC directly or a qualified accountant before filing.
Since HMRC's 2024 rule change requiring marketplaces to report seller sales data, a lot of people selling on eBay, Vinted, Depop, or Etsy have started genuinely wondering whether they owe tax on it. The honest answer depends entirely on how much you're making: under the £1,000 trading allowance, there's nothing to file and nothing owed. Above it, you need to register for Self Assessment — this tool estimates exactly what that would cost you, using current 2026/27 Income Tax and Class 4 National Insurance rates, and correctly accounts for whether you're already employed elsewhere.
It also compares the £1,000 trading allowance against claiming your actual expenses, and tells you which one genuinely results in less tax — they're not always the same answer.
Only if your gross income from selling goes over £1,000 in a tax year. Below that, the trading allowance means there's nothing to report. Above it, you need to register for Self Assessment even if you don't end up owing much tax once expenses are considered.
Your gross income before any costs — the total amount you received from sales, not your profit after expenses. This is a common point of confusion, since people often assume it's based on profit.
Your side-hustle profit stacks on top of your employment income for tax purposes, so it doesn't get its own fresh Personal Allowance. This tool accounts for that by working out the tax your side income specifically adds, not treating it as a standalone amount.