INTM489898 - Diverted Profits Tax: notification, charging and payment: how to notify
You should check the other guidance available on GOV.UK from HMRC as Brexit updates to those pages are being prioritised before manuals.
A notification must be made in writing. It must state which section of the legislation (section 80, section 81 or section 86) applies and must specify the following:
Where the company is potentially within the scope of DPT because it is a company resident in the UK that enters into a transaction where either the transaction or an entity which is party to the transaction lacks economic substance and that results in a tax mismatch, or it is a non-UK company which has a UK-taxable presence (a permanent establishment) and enters into a transaction where either the transaction or an entity which is party to the transaction lacks economic substance and that results in a tax mismatch