https://www.slab.org.uk/guidance/guidelines-for-applying-for-approval-supporting-documents-issues-to-be-addressed-and-costs/
You must use the online application system in all cases to allow us to obtain the basic information needed for a prompt decision.
If you are seeking prior approval in a case of exceptional urgency, apply by telephone, then promptly complete the online application.
With the application for approval, you should send us:
Where you send us lengthy documents, please highlight the relevant passages.
Where the work involves getting an order of the court (for example, specification of documents), you should get our approval before asking the court to consider the matter. You should:
Any application we grant may include a condition that costs may not exceed a specified amount or that specified work may not be carried out.
Before making the application, you should consider whether there is an alternative, more economical way to do the work. This may include considering using technology to reduce expense (video conference to avoid travel for example), or limiting the scope of the work to remove any parts of the work which are not essential to achieve the required outcome (the scope of the proposed work may go beyond what is needed to address the relevant issue).