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What is box 165 on the CT600? (net trading profits)

Reviewed by Lee Jones, Founder · Updated 16 July 2026
The short answer

Box 165 is called "Net trading profits" and it is a simple subtraction: the trading profit you put in box 155, minus any old losses you used against it in box 160. If you have no old losses, box 165 is just the same number as box 155. It can never be a minus number: the lowest it goes is £0.

Official source. This guide is a plain-English summary of official GOV.UK guidance, not advice. The authoritative source is The Company Tax Return guide on gov.uk. Always rely on that over our summary.

What goes in it?

Box 165 does not bring in any new information. It just finishes off a little three-box story that starts two boxes earlier:

  • Box 155, "Trading profits": the profit your company made from its trade this year, after the tax adjustments.
  • Box 160, "Trading losses brought forward set against trading profits": any losses from earlier years, from the same trade, that you are using to shrink this year's profit. If you have none, box 160 stays empty.
  • Box 165, "Net trading profits": box 155 minus box 160. The profit that is left after the old losses have done their work.

Here is the everyday case. Your company made a £20,000 trading profit this year and has no losses from earlier years. Box 155 says £20,000, box 160 is empty, and box 165 says £20,000. The same number appears twice, and that is completely normal.

Now the loss case. Same £20,000 profit, but your company made a £6,000 loss two years ago that has been waiting to be used. Box 155 says £20,000, box 160 says £6,000, and box 165 says £14,000. That £14,000 is the trading profit that carries on through the rest of the form.

And if the old losses are bigger than this year's profit? Say the waiting loss was £25,000. You only enter enough loss to cover the profit, so box 160 says £20,000, box 165 says £0, and the leftover £5,000 keeps waiting for a future year. HMRC's guide is explicit on this: when box 160 equals box 155, you enter 0 in box 165, never a minus number.

What usually goes wrong?

The classic mistake is putting this year's loss near box 165. These three boxes are only for profitable years. If your company made a loss this year, box 155 has nothing in it, and HMRC's guide says to leave box 165 blank in that case; the loss itself is recorded further down the form. Our guide on trading losses and the CT600 covers where it goes.

Two smaller traps catch people too. Box 160 is only for old losses from the same trade; losses being used in other ways go in a different box. And entering the whole loss pile in box 160 when it is bigger than the profit drags box 165 below zero, which is never right.

One honest boundary: if your company's profits run into the millions, or its loss history involves group companies or other complications, there are extra rules that cap how much loss you can use in one year. That is genuinely accountant territory, and paying for an hour of advice is the right move there.

Do I have to work this out myself?

If you are filing with software, no. Any decent filing software does the box 155 minus box 160 sum for you, and your only job is to check the answer looks right. SimpleReturns works these boxes out from your bank statement and a few plain-English questions: your trading profit comes from the statement, you are asked about any old losses in plain English, and the subtraction happens automatically. You see every figure before anything is sent, and filing both the tax return and the accounts costs a flat £99.

If you are checking a return an accountant prepared, the check takes ten seconds: box 165 should equal box 155 minus box 160, and it should never be negative.

Common questions

Box 165 is the same as box 155 on my return. Is that wrong?

No, that is the normal case. It just means your company has no old trading losses in box 160, so nothing was taken off. Most small companies look exactly like this.

My company made a loss this year. What do I put in box 165?

Nothing. Leave it blank. Boxes 155, 160 and 165 only get filled in when this year's trade made a profit. A loss-making year is recorded in the losses section of the form instead.

Does box 165 have to match the profit in my accounts?

Not exactly, and usually it will not. Box 155 is your accounts profit after tax adjustments, and box 165 is that figure after old losses, so a gap between the two is expected, not an error. The gap can be big: if old losses cover the whole profit, box 165 is £0 even though your accounts show a healthy year.

Want the boxes filled in for you?

SimpleReturns works out boxes 155, 160 and 165 from your bank statement and a few plain-English questions, and lets you review every figure before anything goes to HMRC. Filing the tax return and the accounts together costs a flat £99.

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And if your company has group companies or millions in profit, the loss rules get genuinely complicated; an accountant is the right call there, and we say so plainly.

General guidance, not advice. This guide explains how the rules generally work for small UK limited companies. It isn't tax advice for your specific situation, if you're unsure, check with us or an accountant.