CT600 Box 170: Trading Losses Explained

If your company made a trading loss this year, you need to report it in Box 170. This guide explains what goes in this box and your options for using the loss.

What is Box 170?

Box 170 on the CT600 is labelled "Net trading losses" (or "Trading losses" on some versions).

This box reports the amount of trading loss your company made during the accounting period. A trading loss occurs when your business expenses exceed your trading income.

What Goes in Box 170?

Include:

  • Net trading loss from your P&L account
  • Only losses from trading activities
Do NOT include:
  • Property income losses (reported separately)
  • Capital losses (reported in capital gains section)
  • Non-trading loan relationship deficits (Box 255)

How to Calculate Box 170

Step 1: Calculate Trading Result

From your profit and loss account:

``` Turnover £100,000 Less: Cost of sales (£60,000) Gross profit £40,000 Less: Operating expenses (£55,000) Operating loss (£15,000) ```

Step 2: Identify If It's a Trading Loss

A trading loss occurs when:

  • Operating expenses exceed gross profit
  • The loss relates to your main trade

Step 3: Enter the Loss Amount

Enter the loss as a positive figure in Box 170:

Box 170: £15,000 (not -£15,000)

Important: Box 165 vs Box 170

These boxes are mutually exclusive for trading:

SituationBox 165Box 170
Trading profit of £50,000£50,000£0 or blank
Trading loss of £20,000£0 or blank£20,000
Break-even£0 or blank£0 or blank
Never enter a negative number in Box 165. Losses always go in Box 170.

What Happens to Trading Losses?

After reporting the loss in Box 170, you have several options:

Option 1: Set Against Other Income (Current Year)

Your loss can offset other income in the same period:

  • Property income
  • Investment income
  • Chargeable gains
This is claimed in the deductions section of the CT600.

Option 2: Carry Back

You can carry the loss back to the previous 12 months:

  • Must have had profits in the prior period
  • Claim via Box 275 area or separate claim
  • Results in tax refund if tax was already paid

Option 3: Carry Forward

Carry the loss forward to future periods:

  • Offset against future trading profits
  • No time limit on how long you can carry forward
  • Reported in Box 285 (losses carried forward)

Several CT600 boxes relate to losses:

BoxDescriptionPurpose
170Net trading lossesThis period's trading loss
250Losses brought forwardLosses from prior periods
275Trading losses this periodLosses used this period
285Trading losses carried forwardLosses saved for future

How These Boxes Connect

Scenario: You made a £30,000 loss last year, which you carried forward.

This year you make £20,000 profit:

  • Box 165: £20,000 (trading profit)
  • Box 250: £30,000 (losses brought forward)
  • Box 275: £0 (using carried forward losses instead)
  • Box 285: £10,000 (remaining losses to carry forward)
The £30,000 prior loss reduces your taxable profits.

Example Calculations

Example 1: First Year Trading Loss

Situation:

  • New company, first year of trading
  • Made a £25,000 trading loss
  • No other income
CT600 entries:
  • Box 165: £0
  • Box 170: £25,000
  • Box 285: £25,000 (carried forward)
  • Box 410: £0 (no taxable profits)
  • Tax due: £0

Example 2: Loss with Other Income

Situation:

  • Trading loss: £15,000
  • Rental income: £10,000
CT600 entries:
  • Box 165: £0
  • Box 170: £15,000
  • Box 190: £10,000 (property income)
  • Loss offset claimed: £10,000
  • Box 285: £5,000 (remaining losses)
The loss offsets the rental income.

Example 3: Loss Carry Back

Situation:

  • Last year: Paid £10,000 Corporation Tax on £50,000 profit
  • This year: Trading loss of £30,000
CT600 entries:
  • Box 165: £0
  • Box 170: £30,000
Claim:
  • Carry back £30,000 to prior year
  • Prior year recalculated: £50,000 - £30,000 = £20,000 taxable
  • Tax refund expected on excess tax paid

Terminal Loss Relief

If your company is closing:

  • Trading losses in the final 12 months can be carried back 3 years
  • Must be made in the last accounting period before trade ceases
  • Losses set against most recent year first
This can result in significant tax refunds for failing businesses.

Common Mistakes

1. Entering Losses as Negatives

Wrong: Box 165: -£15,000 Right: Box 165: £0, Box 170: £15,000

2. Missing Loss Relief Claims

Problem: Not claiming loss offset against other income Fix: Review all options in the deductions section

3. Overstating Brought Forward Losses

Problem: Claiming more losses b/f than available Fix: Check prior year CT600 Box 285 for correct figure

4. Not Carrying Losses Forward

Problem: Losing track of accumulated losses Fix: Maintain a schedule of losses and update Box 285 each year

Corporation Tax When You Have Losses

Making a loss doesn't always mean zero tax:

  • Other income may still be taxable
  • Only trading losses get loss relief
  • Some reliefs are restricted
However, if your only activity is trading and you made a loss, you'll typically owe no Corporation Tax.

When Using TinyTax

TinyTax automatically:

  • Detects when you've made a trading loss
  • Populates Box 170 correctly
  • Carries forward losses to future periods
  • Suggests loss relief options available

Need Help?

Understanding loss relief can save your company significant tax. TinyTax helps you identify loss relief options and ensures losses are correctly reported and tracked.

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