I got sent £10 note in an envelope yesterday, got me stumped as the SAE's I've left customers ain't for that amount.
I'm assuming it's an £8 house that's left a tip 
Teach me to write the address on the envelopes in future :
I'm shocked most of you don't at least put the the first line of address on the back of an envelope, its so simple and so quick to update.
Each and everyone of my customers has a customer number, when I put a ticket through there door is has there number on it, if they send me a cheque all my custy's write this number on the back of there cheque, I cross reference it on the computer if I don't reconise there name, its so easy.