Beta This part of GOV.UK is being rebuilt – find out what beta means

HMRC internal manual

Business Income Manual

Introduction: about this manual

What the BIM is for

This manual is to help you compute trading income for tax purposes or check calculations. It supplements the basic guidance provided in the self-assessment tax return and help sheets.

It is written primarily for HMRC staff but it can also assist customers and their professional advisers. You are seeing the whole manual with nothing hidden.

You can get basic information on how to compute trading profits from the self-employed notes pages of the tax return and the related help sheets. The helpsheet for customers with annual business turnover of less than £73,000 who need to complete the short version of the self-employed supplementary pages of the return (SA103S) can be found on GOV.UK at The helpsheet for those required to complete the full version (SA103F) can be found at

Agents can also find guidance in the Business Profits Toolkit at

How to use the BIM

The main way to get to the BIM pages you need is drilling down through the contents pages.

We strongly recommend that you study the contents pages of each chapter of the manual to make sure that the further detail is not taken out of context. If you aren’t on a contents page, you can find contents by selecting the ‘Business Income Manual’ link in the breadcrumb trail at the top of each page.


  • HMRC staff can use the feedback page.
  • Anyone using the internet can click on ‘Give feedback about this page’ link in the header box at the top of the page.

What isn’t in the BIM

The BIM includes guidance on most aspects of the computation of trading profits. But some topics are dealt with in more detail in other manuals as follows.

Capital Allowances Capital Allowances Manual
Rules for companies about loan relationships, foreign exchange (FOREX) and derivative contracts Corporate Finance Manual
Rules for companies about the taxation of intangible assets; research and development relief and tax credits; vaccines research relief and tax credits Corporate Intangibles Research and Development Manual
Corporation Tax Company Taxation Manual
Leasing Business Leasing Manual
Rents and other income from property Property Income Manual
Class 4 National Insurance which is payable by the self-employed National Insurance Manual
Self Assessment: the mechanics of assessment of income including trading income Self Assessment Manual