Your business must registered with HMRC if it carries out work described as estate or letting agency activity.
You must register if you (a) have clients who want to buy, sell or rent an interest in land, and you introduce them to third parties who want to correspondingly buy, sell or rent that interest in land; or (b) secure the sale or purchase of that interest in land after an introduction is made. This land can be within or outside the UK.
These activities include:
For example, high street residential letting agents, commercial letting agents, online letting agents and property auctioneers must all register. For more information on what businesses must register view the government guidance here.
A letting agent does not need to registered if they handle less than 10,000 euros of rent per month. Other exceptions are listed here.
If you fail to register where you are so required, you may receive a penalty. You must remember to renew your registration and if you are no longer required to register then notify HMRC.