H M Revenue & Customs have created a Trust Registration Service. It is now a requirement of all express trusts (with a few exceptions) to be registered with them. Further details about whether the Trust should be registered with H M Revenue & Customs can be found here.
Trusts that should register, and were created before the 6th October 2020, even though they do not have a tax liability, must register by the 1st September 2022.
Trusts that should register and were created after the 6th October 2020, even though they do not have a tax liability, must register within 90 days of being created (or the date of when the Trust became registerable) or by 1st September 2022 (whichever is the later)
If the Trust is taxable then you should take advice from a suitably qualified tax adviser to ensure that your necessary reporting obligations are being complied with by the necessary specified deadlines to avoid penalties and interest being incurred. If you are not sure whether a Trust is taxable then you should still take advice from a suitably qualifies tax adviser to confirm the position.