CTSA: introduction: differences from ITSA
You should check the other guidance available on GOV.UK from HMRC as Brexit updates to those pages are being prioritised before manuals.
There are also some important differences between CTSA and ITSA.
Under CTSA, companies continue to be chargeable to CT rather than IT.
CT continues to be charged in a single amount on the sum of ‘profits’. This means income, computed under the same principles that apply to IT, and chargeable gains, computed under the principles that apply for CGT.
Tax under CTSA continues to be charged by reference to accounting periods. The length of an accounting period can vary with circumstances, and the company controls the end date, though no accounting period can exceed twelve months. By contrast, IT is always charged for the tax year ending 5 April.
CT rates and limits are imposed for ‘financial years’, which begin on 1 April and end on 31 March following. For example, the financial year 2018 is the year from 1 April 2018 to 31 March 2019. By contrast, IT is charged for each tax year beginning on 6 April.
Companies cannot opt for HMRC calculation of their tax, whereas individuals can do so.
For many companies there continues to be a single, fixed due date for payment of CT. This is nine months and one day after the end of the accounting period. Large and very large companies are subject to instalment payment regimes.
The notice to deliver a company tax return continues to require the submission of such information, accounts and computations as may reasonably be required by the notice, as well as the return form.