https://www.slab.org.uk/guidance/submission-of-account-of-expenses-when-must-your-final-account-be-submitted-by/
You must send us your account and completed synopsis no later than four months after the date of completion of the proceedings for which civil legal aid was granted. Completion of proceedings includes work in connection with obtaining an award of expenses, modification of expenses, settling with the witnesses, obtaining an extract of decree etc.
We may accept an account submitted later than four months if we consider there is a “special reason” for late submission. Possible reasons include:
We would be unlikely to accept forgetfulness or understaffing as special reasons for late submission.