Trading Losses & Corporation Tax: How to Claim Relief on Your CT600
If your limited company makes a trading loss, you don't just absorb it — HMRC offers several ways to use that loss to reduce your Corporation Tax bill. Getting this right can save your company thousands.
Types of Loss Relief
1. Set Against Current Period Profits (s37 CTA 2010)
Your trading loss can be set against all profits of the same accounting period — not just trading profits. This includes investment income, chargeable gains, and property income.
This is usually the first option to consider because it gives immediate relief.
2. Carry Back (s37(3)(b) CTA 2010)
After setting the loss against current period profits, any remaining loss can be carried back to the previous 12 months and set against total profits of that period.
If you've already paid Corporation Tax for the carry-back period, HMRC will refund the overpayment.
Example: Carry Back
| Period | Profit/Loss | Tax Position |
|---|---|---|
| Year ending 31 March 2025 | £50,000 profit | CT paid: £9,500 |
| Year ending 31 March 2026 | (£80,000) loss | No CT due |
The £80,000 loss is carried back against the £50,000 profit. HMRC refunds the £9,500 CT already paid. The remaining £30,000 loss carries forward.
3. Carry Forward (s45A CTA 2010)
Losses not used in the current period or carried back can be carried forward indefinitely. From 1 April 2017, the first £5 million of carried-forward losses can be used each year without restriction. Above £5M, losses are restricted to 50% of profits.
CT600 Boxes for Losses
Loss claims and loss records appear in several boxes on the CT600, depending on the type of relief being claimed:
| Box | Description |
|---|---|
| Box 160 | Brought-forward losses from earlier periods set against trading profits (same trade only) |
| Box 275 | Current-period losses set against total profits (s37 relief); also used when losses are carried back from a later period |
| Box 280 | Tick (X) if box 275 includes losses carried back from a later accounting period |
| Box 285 | Post-April 2017 losses carried forward, claimed against total profits (s45A) |
| Box 780 | Total trading loss for this period — records the loss in the losses section for carry-forward |
Box 160 lets you apply old losses specifically against this year's trading profits. You can enter at most the amount in box 155 (trading profits) — you cannot create a further loss using brought-forward losses.
Box 275 is broader: it sets a current-period loss against your company's total profits (trading income, interest, property income, chargeable gains). This is where a current-year s37 claim goes. If a loss from a later accounting period is being carried back to an earlier return, tick box 280 to tell HMRC.
Box 285 is for the flexible post-2017 carry-forward: old losses (arising after 1 April 2017) set against total profits, not just trading profits. Note the £5M annual cap — losses above that are restricted to 50% of profits.
Box 780 records the amount of the trading loss arising in this period — the raw figure that HMRC will allow to be carried forward.
4. Terminal Loss Relief (s39 CTA 2010)
If your company ceases trading, losses from the final 12 months can be carried back up to 3 years (not just 12 months).
5. Group Relief (s99 CTA 2010)
If your company is part of a 75% group, trading losses can be surrendered to other group companies to offset their profits.
Common Mistakes
- Not claiming loss relief at all — HMRC won't apply it automatically
- Claiming carry-back without current-year relief — you must use s37 first
- Mixing capital and trading losses — capital losses can only offset capital gains
- Missing the time limit — claims must be made within 2 years of the loss-making period end
- Forgetting to file — you must file a CT600 even if you make a loss
Using brought-forward losses or setting a current-year trading loss against total profits? File your CT600 with Taxpipe — both reliefs are handled automatically in our guided wizard. £59, no hidden fees.