This part of GOV.UK is being rebuilt – find out what beta means

HMRC internal manual

Stamp Duty Land Tax Manual

Scope: What is chargeable: Contract and conveyance: Definitions FA03/S44

A contract includes any agreement.

A conveyance includes any instrument whether in written or electronic form including a lease.

Completion means the completion of the land transaction proposed by the contract between the same parties in substantial conformity with the contract.