Updating post from Reddit.
The "Certificate of Lawfulness" covers planning, and that remains unchanged; you don't need to take any action on it. Obtaining a copy of the current owner would be useful for the file.
The "HMO Licence" needs to be reapplied for in your name; however, it shouldn’t be unreasonably withheld, as it already exists. They will want to carry out checks on you and may need to re-inspect the property. So, some minor works might be required.
If there is an Article 4 direction, it’s likely that the council also requires individual landlords to be licensed.
Buying Tented Properties carries risks; purchasing a 3-bedroom HMO multiplies that risk threefold. You depend on the existing landlords to pre-vet properly, which may not always be ideal, and they must have served the correct notices and contracts, secured the deposit, and provided the necessary information on Electric, EPC, and Deposit, among other things. Failing to do any of these could make it difficult for you to evict if needed. Your solicitor can address all these issues with retentions or guarantees.
You need the right mortgage, an HMO Mortgage or an HMO for SPV Mortgage - your typical BTL mortgage will not be suitable, and the Local Authority writes to them as part of your licence application.
Hope this helps.
I am buying a HMO in a London, article 4 area. I have the HMO license from the soon to be ex owner prior to article 4 coming into place. Do i need to do anything with planning or get a certificate of lawfulness?.
The estate agent selling the house says there is no need to get into planning since i can prove it was used as a HMO prior to article 4 coming into place.
The proof i have is the seller's HMO license
That's not strictly accurate; a HMO Licence, Selective Licensing, and Planning are three different things - council departments don't often communicate with each other. So, it is possible to have a HMO Licence without Planning.
However, if they have a "Certificate of Lawfulness" related to planning and you know they possess an HMO Licence (which you can verify from the database), then it should be fine.
P.S. Don't take advice from the "Sellers Letting Agent". They work for the other side, not you. Your conveyancing solicitor and mortgage adviser are your sources of advice (& a buying agent, but no one uses them).