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HMRC internal manual

Labour Provider Guidance

Systems and processes: HMRC information systems: direct tax: COTAX


COTAX is the Company Tax computer system that deals with the assessment and collection of Corporation Tax (CT).

It is a ‘process now, check later’ system. Companies are required to file returns and pay tax by prescribed dates. HMRC then has a fixed period in which to begin an enquiry to check the accuracy of a return.

COTAX roles and access

The COTAX role you are allocated is determined by your job role and grade. All roles are allocated via your manager using SRS.

Access to COTAX is via My Services / Corporate Services / ISSO.

Each office to which COTAX is allocated has a Management Unit ID (MUID). The MUID where a company’s record is held is determined by postcode.

From 1 April 2011 most companies have had to file their company tax returns online for all Accounting Periods ending on or after 1 April 2010. This includes the accounts and computations elements of such returns.

If you need to view an online return, including the attachments, you will need to have the following user roles allocated to you:

  • IR Portal role
  • Any COTAX role in the MUID (office) to which the record belongs.

This could mean that you will need multiple roles in COTAX to see all the returns you need to view.

COTAX and Labour Providers

Information that can be obtained from COTAX includes the following

  • Corporation Tax Return entries - declared turnover can be a useful tool as a comparison to submitted information on VAT Returns.
  • Corporation Tax Return filing history
  • Payment and debt information
  • Assessments
  • Company details
  • Agent details

COM - COTAX Manual - Provides procedural help in using the COTAX system and technical/background information and Corporation Tax

COTAX System Help (COSH) - Instructions on the use of functions in the COTAX system. You can access COSH by using the Help button available on each COTAX screen, or by pressing the F1 Key

COTAX Business Help Desk - Help with problems you come across when you’re using COTAX