How to claim intangible amortisation or impairment on a CT600

1. Enter the trading accounting charge

Open Financial data. Match each amount in your prepared accounts and tax working to the appropriate row below.

Trading accounting charge

Profit & loss → Trading income and expenses → Depreciation and amounts written off assets

Include the full prepared charge in this total. Do not repeat it in Other charges.

Trading tax deduction

Tax adjustments → Intangible amortisation or impairment deductible (Part 8 CTA 2009)

Enter the qualifying part of that accounting charge, as determined by your tax working.

Property accounting charge

Profit & loss → Property income and expenses → Depreciation and amounts written off assets

Enter only the property share here.

Property tax deduction

Tax adjustments → Property tax treatment → Property qualifying intangible amortisation or impairment

Enter the qualifying property share once. For both activities, keep the two shares separate.

Open Financial data, then Profit & loss. Under Trading income and expenses, include the charge in Depreciation and amounts written off assets. This total can contain tangible depreciation as well as intangible amortisation and impairment. Do not also include the same charge in Other charges.

2. Enter your prepared tax deduction

In Tax adjustments, use Intangible amortisation or impairment deductible (Part 8 CTA 2009). Enter one combined qualifying accounts-based deduction. For example, £1,000 qualifying amortisation plus £2,000 qualifying impairment means a single entry of £3,000.

The field restores relief after the automatic depreciation add-back. Its amount must be included in the corresponding depreciation figure and cannot exceed the available total. This is the limit of this input, not a statement that every Part 8 deduction is calculated in this way.

Partial deduction example: your prepared accounts contain a £2,000 impairment and your tax working gives a £1,500 deduction. Include £2,000 in the accounting charge and enter £1,500 in the deduction field. The £500 difference stays added back for tax. These figures illustrate entry only, not an assumed tax percentage.

3. Keep the property share separate

For property activity, enter its accounting charge in Depreciation and amounts written off assets under Property income and expenses. Enter its prepared deduction in Property qualifying intangible amortisation or impairment, under Property tax treatment in Tax adjustments.

A company with both activities enters each share in its own fields. A property-only company uses the property fields. Do not duplicate a deduction in trading and property. Read the property income guide for the existing property tax-base override.

4. Check the review and computation

At Review, check the accounting charge, deduction and resulting profit or loss. The trading line is Less: intangible amortisation or impairment (Part 8). Property deductions appear in the property reconciliation. Generate a fresh draft and check the same amounts in the tax computation.

For a short period, enter prepared figures for that Corporation Tax period. If the filing produces two CT600s, the existing time-apportionment calculation divides this deduction. Check each return and computation. This field does not offer a separate transaction-based allocation.

5. What appears on the CT600

CT600 box 640 indicates that the company has written down or sold intangible assets. HMRC asks for it for trading, property and non-trading assets. The indicator does not change the tax due. Read HMRC's box 640 guidance.

We tick box 640 automatically on a return whose computation includes a positive accounts-based Part 8 deduction, including the property share. You can see the tick on the CT600 form PDF. If your filing produces two returns, the deduction rule applies to each return. You can also report a sale or a write-down with no deduction by answering the intangible asset event question and selecting the relevant return. Generate a fresh draft and check both forms before submitting.

A sale or write-down can require box 640 even with no allowable deduction. Use the event question for that case. Do not enter a tax deduction just to make the box tick. The sale and write-down guide explains the separate accounts and tax entries.

6. Check the treatment before choosing the field

This field covers the supported accounts-based deduction, not fixed-rate relief or disposal and other realisation debits or credits. A write-off is not automatically an impairment or a fully deductible expense. Use the treatment in your prepared tax working. If it is a realisation, use the separate realisation fields under Tax adjustments.

For intangibles the company held before 1 April 2002, check HMRC's Part 8 scope rules and exceptions. For goodwill or customer-related intangibles bought on or after 8 July 2015, check the restrictions for the acquisition date. Relief can be restricted or use a fixed rate which this field does not support.

Read when amortisation can be deductible and impairment of a franchise or software licence. HMRC explains the conditions in CIRD12755 and business-use allocation in CIRD13520.