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HMRC letter codes · Corporation Tax (CT)

CT631Group Payment Arrangements Apportionment Notice

Last reviewed 14 October 2026 · How Tax Letters checks its facts

In short

HMRC's internal manual forms index describes the CT631 as a notice issued by the Group Payment Team if the nominated company does not respond to a Closure Notice within 30 days of its issue, showing how HMRC will apportion payments made for the Group Payment Period against the participating companies' accounting periods.

“A notice issued by the Group Payment Team if the nominated company does not respond to a Closure Notice within 30 days of its issue. The notice shows how HMRC will apportion payments made for the Group Payment Period (GPP) against the participating companies APs for the GPP.”

HMRC COTAX Manual: COM150, Forms index · checked 14 October 2026

Information, not advice: this page reports what HMRC, GOV.UK and the bodies named publish about CT631. Each fact has its source and the day it was checked beside it.

What it is

HMRC's CT630 and CT631 notes say the Apportionment Notice (form CT631) shows how HMRC intends to allocate the group payments in the absence of a reply to the Closure Notice.

“Apportionment Notice form CT631 … This shows you how we intend to allocate the group payments in the absence of your reply to the Closure Notice.”

GOV.UK: Group Payment Arrangements: CT630 and CT631 Notes · checked 14 October 2026

What it asks

HMRC's CT630 and CT631 notes say that if you do not agree with the allocation on a CT631 and want to amend the apportionment, you must tell HMRC, within 30 days of the date shown on the Apportionment Notice, how you want it to allocate the payments.

“If you don’t agree with the allocation and want to amend the apportionment you must tell us, within 30 days of the date shown on the Apportionment Notice, how you want us to allocate the payments.”

GOV.UK: Group Payment Arrangements: CT630 and CT631 Notes · checked 14 October 2026

Free help and HMRC contacts

For advice about Group Payment Arrangements, including about a CT631, HMRC's advice line (GOV.UK) is 03000 583 947, open Monday to Friday, 9am to 4pm and closed on bank holidays. GOV.UK says to have the Group Payment Arrangement reference number to hand when calling, and has a “Find out about call charges” link.

“Call for advice about Corporation Tax Group Payment Arrangements. Have your Group Payment Arrangement reference number with you when you call. … Telephone: 03000 583 947 Opening times: Monday to Friday: 9am to 4pm. Closed bank holidays … Find out about call charges”

GOV.UK: Corporation Tax Group Payment Arrangements: enquiries · checked 14 October 2026

Free help first

These routes are described by GOV.UK, TaxAid and Citizens Advice themselves.

  • HMRC's extra supportHMRC offers extra support if your health condition or personal circumstances make it difficult to contact HMRC, for example a mental health condition, financial hardship or being treated in hospital.
  • Someone to deal with HMRC for youYou can authorise a friend, relative or voluntary organisation to talk to HMRC for you and help you fill in forms.
  • TaxAidTaxAid helps people with tax problems who cannot pay for advice. Tax Help for Older People merged with TaxAid in July 2025.
  • Citizens AdviceCitizens Advice gives confidential advice online, over the phone and in person, for free.