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HMRC internal manual

COTAX Manual

Background: features of COTAX: introduction

COTAX is the Company Tax computer system that was introduced on 10 November 1999 to deal with the CT Self Assessment (CTSA) legislation enacted on 1 July 1999. It also deals with the previous CT Pay and File (CTPF) legislation.

Before the introduction of COTAX, there was a CTPF computer system which was introduced on 1 October 1993 and before that, CT was assessed using the CTA / CTC part of the IRIS computer system. The CTPF system was decommissioned when COTAX was introduced, and CTA / CTC was decommissioned in November 2010.

COTAX System Help (COSH) is available to guide you when you are using COTAX functions.

This section of the COM gives you information on specific features of COTAX.