https://www.slab.org.uk/faqs/is-there-a-time-limit-to-send-you-notification-that-ive-granted-aa-for-police-station-advice/
You have 14 days from the date of the first item of work to register the grant of A&A. We’ll issue a reference number immediately. You then have 12 months from the last valid work item on your account to submit your claim for payment.