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HMRC internal manual

COTAX Manual

HM Revenue & Customs
, see all updates

Accounting periods: company accounting periods: maintaining the AP record

This subject is presented as follows.

Enforcement proceedings
Logged returns
Revised filing dates
Using function MAPD
Difficulties with function MAPD
Linked APs


Companies with a well established business normally have a regular pattern of annual APs. COTAX maintains the record automatically by creating a new AP each time it issues a notice to deliver a return. Where you need to change the AP structure, you use function MAPD (Maintain AP Dates).

You can view the current AP structure and AP linking using function DAPD (Display AP Details).

Before making any changes to the company record, you must always consider the current AP record and examine the company’s assessing, payment, and returns position. You are then fully aware of any possible complications relating to:

  • stranded assessments, payments and returns on APs you supersede
  • AP links that already exist and may be changed by your action.

In MAPD you can change the following details.

  • AP start and end dates.
  • Enter a new AP before COTAX automatically creates one.
  • Record periods of dormancy and exemption. See COM1110 for more information.

The function also shows you any AP links which will be created and any additional actions you must take on superseded APs as a result of your amendments.

Enforcement proceedings

If you are going to amend an AP for which proceedings are being taken for amounts overdue, you must tell the appropriate Debt Management and Banking office or the Enforcement and Insolvency Service (EIS).

Logged returns

You can only amend the start or end date of an AP with a logged return where there is an open appeal for the AP.

For example, a company may appeal against a revenue amendment in a closed enquiry case. The settlement of the appeal by agreement or determined by the Tribunal could include a change of AP. COTAX allows you to amend the AP which is ‘open - under appeal’ without unlogging the return.

In all other cases, you must unlog the return first using function URTN (Unlog Return). You can find full details of how to do this at COM130000 onwards.

You must make sure that you unlog the return and amend the AP record on the same day to prevent COTAX issuing an incorrect notice to deliver, reminder or penalty.

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Revised filing dates

If an AP forms part of a period of account ending after the end of the AP, the filing date (Word 42KB) is normally 12 months after the end of the period of account. COTAX cannot automatically implement this rule.

Whenever you use MAPD (Maintain AP Dates) to deal with these cases, you must also use function RDAC (Record Filing Date Adjustment), to record a revised filing date. There is a reminder on the final screen in MAPD prompting you to do this.

COM130210 has more information on revised filing dates.

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Using function MAPD

The MAPD (Maintain AP Dates) screen displays a maximum of five APs or periods of dormancy or exemption, beginning with the period you selected. You can create records for a maximum of five new periods.

The start date field of the first revised period is pre-populated with the start date of the period you selected.

When you amend or add AP records, validation makes sure that COTAX holds a continuous sequence without gaps or overlaps.

You must not create live APs, dormancy or exempt periods far into the future. You only need to create an AP ending on or after the date on which you are using the function. Each month, COTAX identifies APs that have ended, issues a notice to deliver and creates the following live AP.

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Difficulties with function MAPD

There are two situations when you have to use function MAPD (Maintain AP Dates) twice in succession to make the amendments you require. These are where you need to amend more than five existing APs or create more than five new AP records.

Difficulties using MAPD - Example (Word 45KB)

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Linked APs

When creating new APs that overlap existing APs, COTAX automatically tries to link a superseded AP with an appropriate superseding AP ending in the same link period (Word 28KB).

This linking allows COTAX to:

  • move payment postings from a superseded AP
  • identify a revenue determination superseded by a self assessment, where the determination and the assessment are for different periods
  • find and reinstate the determination if the return is subsequently unlogged.

If COTAX cannot make the links automatically, it shows you a list of superseded and superseding APs for you to link manually.

CTSA does not copy self assessment details from superseded to superseding APs but does transfer AP record postings and inhibition signals.


  • COM1180 for guidance on amending APs for which CTSA assessments have been recorded
  • COM1041 for a list of forms relevant to this subject
  • COM1021 for a list of functions to use in particular situations
  • COM1022 for legislation applying to this subject.