https://www.slab.org.uk/guidance/procedure-for-withdrawing-from-giving-advice-and-assistance-civil/
If you wish to stop giving advice and assistance to your client you must:
Advice and Assistance application procedures
This page includes information on how to apply for non-templated increases in expenditure under civil A&A. It covers the information you should provide us with; case-related factors to address in your application; the process for reconsideration of refused increases; the process for urgently needed increases; whether authority for retrospective increases is available; and other guidance you may wish to consider.