What Is a Completion Certificate?
Written by James Walker · Last reviewed 15 August 2026
James Walker has 2 degrees in construction (BSc (Hons) Building Surveying · MSc Environmental Design of Buildings) and an extensive background in issue resolution, resolving over £4 billion of consumer issues.
A completion certificate is issued by building control to confirm that work requiring Building Regulations approval has been inspected and complies. It is the document requested when you sell the property.
Why it matters commercially
This is the practical point most people miss until conveyancing.
Work carried out without the necessary approval and certificate becomes a problem at sale. Buyers' solicitors ask. Options at that stage are retrospective regularisation, indemnity insurance, or a reduced price, all of which cost more than getting it right at the time.
What needs it
Structural work, extensions, loft conversions, many alterations, and certain electrical, heating and window work. Some of it can be self-certified by registered installers rather than going through building control directly.
Planning permission and Building Regulations approval are different things, and needing one does not mean needing the other.
Whose job it is
Establish this before work starts. The builder usually applies and arranges inspections, but confirm it explicitly and confirm the fees are in the price.
Hold your final payment until the certificate exists. It is the clearest example of paperwork being part of what you bought.
How it works
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