What the threshold is measuring
The test is your qualifying income: self-employment and property turnover before expenses, from the tax return you filed in the previous tax year. Over £50,000 in 2024-25 means you are in from 6 April 2026, over £30,000 in 2025-26 from 6 April 2027, and over £20,000 in 2026-27 from 6 April 2028.
Because it is turnover and not profit, a year of expensive parts or a new analyser does not take you back under the line.
The records the job already produces
- The invoice, which is the income record, with labour and parts separated if you want the breakdown later
- The parts and materials you buy, which are expenses with the receipts behind them
- Mileage to and between jobs, which is a record of its own
- Certificates issued on the job, which stay with the job record
- Insurance, registration, tool calibration and test equipment, which are annual costs rather than job costs
Certificates are records too
A gas safety certificate has its own rules about who gets a copy and when, and our guide on CP12s covers that separately. For your own books the useful habit is to keep a copy with the job rather than in a second filing system, so the paperwork the landlord asks for and the record your tax figures come from are the same file.
What each quarterly update contains
| What it is | Where it goes |
|---|---|
| Labour, servicing and call-outs | Self-employment turnover |
| Boiler parts and fittings re-charged | Turnover, with the cost claimed as an expense |
| Van, fuel and mileage | Vehicle costs, or the mileage rate |
| Test equipment, calibration, registration | Other business expenses |
| Insurance and certification costs | Other business expenses |
Each update is cumulative from 6 April, so it is four reviews a year rather than four separate sets of books. A quiet quarter, or a quarter where you only bought stock, still has to be sent, even if some categories are zero.
What to do first
- Work out which cohort you are in from your turnover, not your profit
- Check your accounting period in the software before the first update, because it locks in after that
- Photograph receipts as you go, so the parts you bought are already recorded against the job
- Keep certificates with the job, so the compliance file and the tax file are one thing