Income
Turnover is what your work brought in. If contractors take CIS off your payments, turnover is the full amount before the deduction. The deduction itself is not part of the update, because HMRC gets it from the contractors.
Other income is business income that is not from your sales, such as a grant to the business.
Expenses
Your allowable business costs, added up under HMRC's headings, such as materials and stock, or car, van and travel. Personal spending stays out, and a cost that is part personal goes in at its business part only.
Profit so far
Income less expenses, for the year to the end of the latest quarter. When expenses are higher it shows as a loss. HMRC may use your updates to show an estimate of your tax in your HMRC online account. It is an estimate, not a bill.
What is not in it
Rent from property goes in a separate update. A car or van you claim for, and other year end adjustments, are claimed on your tax return after the year ends.
Lekhio works it out. Lekhio does not send to HMRC yet: you send it.
Where HMRC says it: HMRC guidance on Making Tax Digital for Income Tax, what goes in an update; HMRC's Self Employment Business API, the cumulative period summary. Checked 2026-10-16. This is general information about the rules, not advice on your own position.