What the certificate establishes
The council assesses a legal question, not whether it likes the design. A proposal which complies with an available permitted development right can be certified even though a normal planning application would involve a different assessment. Conversely, an attractive proposal cannot receive a certificate merely because it seems reasonable if the claimed legal basis is missing. [1][3]
The certificate identifies the land and the particular operations or use. The description, plans and relevant date matter. It is not an open-ended permission for whatever later work takes place at the address. [1]
There are two different applications
A proposed-development certificate, often called a CLOPUD, considers whether the operations or use would be lawful if begun at the application date. An existing-development certificate, often called a CLEUD, establishes the lawfulness of a use, operations already carried out or a specified breach of planning condition. [3][4]
Do not choose the existing route merely because part of the project has started, without identifying exactly which works are complete and which remain proposed. The application needs a precise description of the legal question being put to the council. [1]
When is it useful?
A certificate can be useful where the project depends on technical permitted development limits, a disputed original-house baseline or a clear record for a future sale. Planning Portal guidance notes its value in providing evidence to prospective purchasers. It does not guarantee a sale or replace the buyer's wider checks. [5][6]
For a proposed project, assemble drawings showing the relevant existing and proposed arrangement, measurements and planning restrictions. Explain the permitted development provision relied on and provide the information needed to establish compliance. For existing development, the relevant historic evidence depends on the legal basis claimed. [1]
What it does not replace
A certificate is not building regulations approval, listed building consent or a determination of private property rights. Nor can it bypass an outstanding prior-approval requirement attached to a permitted development right. Each necessary part of the lawful planning route still has to be satisfied. [1][7]
Proposed certificates also do not freeze the law indefinitely. Section 192 preserves the effect of the determination subject to a material change, before the use or operations begin, in matters relevant to lawfulness. Re-check the position where a start is delayed and a new restriction may have intervened. [3]
How the council considers it
The applicant must provide enough information to establish the claim. Government guidance says there is no statutory requirement for neighbour consultation on a certificate application, although the council may seek relevant factual evidence. A neighbour's disagreement with the design is not the same as evidence that the legal test fails. [1]
If a certificate is refused, read the reasons carefully. Refusal may reflect inadequate evidence rather than establish that no lawful case could ever be made. A better-supported application or an appeal may be appropriate, depending on the issue. [1][8]
Keep the issued certificate and its referenced plans together. They are the record against which the claimed planning lawfulness needs to be understood.