How are boxes 326, 327 and 328 populated on a CT600?

This article will go through how boxes 326, 327 and 328 are populated on a CT600 return for associated companies.

Firstly, you should review HMRC's company tax return guide to confirm if entries are required in these boxes. An extract has been provided below for your convenience:

326 Number of associated companies in this period

You must enter the number of companies associated with your company for any part of the accounting period if either the:

• company’s profits are chargeable at the small profits rate
• company is entitled to Marginal Relief

The figure should not include your company.

You should also read the note to boxes 327 and 328. If box 326 is completed, do not complete boxes 327 and 328.

For accounting periods ending on or after 1 April 2023, large and very large companies must complete this box with the number of associated companies at the end of the previous accounting period. The figure should not include your company.

Find out more about associated companies by reading the Company Taxation Manual (CTM03900).

For more information about large and very large companies, read regulation 3(7) of the Corporation Tax (Instalment Payments) Regulations 1998.

327 and 328 Number of associated companies in the first and second financial years

Make entries in boxes 327 and 328 instead of box 326 if the:

• accounting period straddles 2 financial years
• upper or lower limit has changed
• number of associated companies was different in each of the financial years

The figure should not include your company.

To begin data entry in TaxCalc, please browse to the below locations:

SimpleStep Mode - CT600 Core > Corporation tax chargeable

HMRC Forms Mode - CT600 Core > Core > Page 4

Box 326 - Number of associated companies in this period

This box shall be locked if the period straddles 1st April 2023 as boxes 327 and 328 should be used OR if the accounting period end is prior to 01/04/2023 as these boxes are only to be used when the rate of corporation tax has changed.

Box 327 - Number of associated companies in the first financial year

This box should be used for any periods that straddle 1st April 2023

Box 328 - Number of associated companies in the second financial year 

This box should only be used for any periods that straddle 1st April 2023

If you are receiving an error in regards to boxes 327 and 328 and there are no associated companies, please enter a 0 into both boxes. As per the screenshot below even though both boxes are red, you are still able to make an entry.

Once a 0 has been entered in both boxes, the error you are receiving will be cleared.