The Mock Turtle

I stupidly had a moment's lapse of concentration a few days ago and reversed into another car's bumper while parking and cracked the number plate. I left a note and they have contacted me and said they'll get a quote for getting a new one. If I just pay them directly which seems easier would you want anything in writing to confirm what this was for and if so, what should it say?

Thanks for this! They've finally got back to me with the cost so I'll look up some appropriate wording unless anyone has done this before and knows a good way to phrase it?