https://www.slab.org.uk/faqs/transfers-of-solicitor-procedure-for-submitting-your-account-and-how-we-must-apportion-fees-where-there-is-a-transfer-of-solicitor/
As the block fees cannot be paid until a block of work is actually completed (and in the case of communications, preparation or post-conviction) that will mean the case must have concluded you cannot submit your final account when your involvement comes to an end if you are not the last acting agent.
You should use the streamlined interim payment process to make a claim for any fees or outlays (excluding mileage) prior to the case concluding. No account is required for interim fee claims but if you wish you can use our online accounts system to create a draft account to assist you in calculating the fee that you expect to be paid.
We will send a notification to all outgoing agents who have acted in a case when the last acting agent has submitted their final account. It is only at that time will we be able to determine what fee is payable to each solicitor. The assessment officer responsible for assessing your claim will liaise with you, where necessary, to ensure that you are being paid the correct amount due.
Paragraph 18 of the Notes on the operation of schedule 1A, sets out the rules which apply where there is a transfer of solicitor.
Where agency is transferred from one solicitor to another—
(a) the fee for a block of work commenced and completed by the same solicitor is payable to that solicitor;
(b) the fee for a block of work commenced by one solicitor but completed by another is to be apportioned equally between the solicitors who undertook work falling within that block.
We have no discretion to apportion a fee on any other basis.
It is important to note that the payment is apportioned where there is a transfer of solicitor. So in circumstances where agency was transferred from solicitor A to Solicitor B and back to solicitor A there is still only two solicitors and the fees would be apportioned 50/50 in such cases rather than on a 2/3rd and 1/3rd apportionment.
The block fees, with the exception of the block in relation to perusal charges, are only payable once in a case.
The block fee for perusal is payable to each solicitor in the case except where the transferee solicitor is considering any documentation that has already been made available and perused by the transferring solicitor in circumstances where:
Although no block perusal fee can be claimed in such cases the incoming solicitor will charge their account for proceeds of crime work on the basis of the detailed fees prescribed under Part 1 of schedule 1A. So they can still charge for the perusal of new material that is disclosed in respect of the proceeds of crime along with any other charges for work reasonably done.