https://www.slab.org.uk/guidance/aa-accounts-and-increases-authorised-level-of-expenditure-not-automatically-payable/
If we allow an increase in authorised expenditure, this is based solely on the information, including likely costs you give us. In granting the increase, we do not necessarily accept that any fee or claim ultimately made by an expert or other witness within that limit is reasonable.
The authorised increase is an upper limit of authorised expenditure within which you can proceed. It is not a guarantee that we will pay a claim to that level. You still have to justify the expenditure in your account.
In certain circumstances, you may wish to discuss the fee with our accounts assessment area before proceeding.
You should:
When you apply for an increase, the costs of any outlays should include VAT.