AAT Unit 18 is about preparing tax computations for businesses and completing the relevant tax returns.
The first element requires preparation of capital allowances computations, including adjustments for private use by the owners of the business.
The second element is about preparation of assessable business income computations for partnerships and self-employed individuals. This includes identifying the NI contributions payable.
The third element is about preparing capital gains computations for companies and unincorporated businesses.
The final element requires candidates to prepare Corporation Tax computations for UK resident companies.