There is a new s21, it is form 6A, and a copy can be downloaded from https://buff.ly/2AZycXF
The 6A is for all tenancies that commenced on or after 1st October 2015, but can also be used for earlier tenancies if you wish, although I don’t think it’s an advisable thing to do. The 6A is only valid for six months from the date of service and it advises the tenant that if you have not served them with a valid Energy Performance Certificate, the Government’s ‘How to Rent’ guide and a Gas Safety certificate (if the property has a gas supply) then a valid notice cannot be served. Any deposit taken should also be protected in a Tenancy Deposit Scheme as part of the new rules. Taking the time to get these key things right will mean that you should be able to secure possession of your property without too much trouble if you wish to. You should also be aware that the 6A will be the correct notice to serve for all tenancies no matter how old from 1st October 2018.