A customer says I damaged their property. What do I do?

Do not admit liability in writing without speaking to your insurer first. Inform your insurer immediately — this is what your £1M (or £2M) PL cover is for. Cooperate with Get Trady: we'll provide the customer with your insurance certificate and your insurer's claims contact, and the job's funds will remain held by Stripe pending the outcome of the insurance claim. If the damage was genuinely not caused by you, document why — photos of the area at the time you arrived, time logs, customer messages confirming the condition of the area.