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

HMRC internal manual

Trusts, Settlements and Estates Manual

Trusts for particular purposes: flat management companies - notification from company's tax office

Where you receive a notification from a tax office dealing with the company’s corporation tax, that a flat management company trust has been identified, you should set up a new record, and issue any trust SA returns that are required.

The corporation tax office will advise you as to the date from which trust liability first arises, and this can be from any date in the tax year.

If for example the CTSA return covers the accounting period to 31 August 2017, the first period of trust SA liability will be the part year from 1 September 2017 to 5 April 2018.