What should I do after losing a cheque that was written out to me in the UAE?

Report it on both fronts, in the right order. First, tell the client immediately and in writing — they are the drawer, and their bank can stop payment on a lost cheque once instructed; loss is a legitimate ground for stopping payment in the UAE. Ask them to do it the same day and to confirm it to you. Second, file a police report recording when and roughly where the cheque went missing. The report protects you in two directions: it documents that the cheque left your hands innocently if someone else tries to present it, and it gives the client and the bank the official paper they often want before a replacement is issued. Then put the replacement request to the client formally. The payment obligation for your freelance work does not vanish because a piece of paper did, and once the stop is confirmed there is no double-payment risk for them to hide behind. Keep copies of everything — the invoice, the report, the stop-payment confirmation, your messages. If the client keeps dragging their feet after that, a formal demand from a licensed UAE lawyer usually ends the stalling, and the underlying debt remains enforceable in court if needed.