We often need a few pounds in change (tooth fairy, school fairest/disco/party, church donations, dh gets a raffle ticket at the football etc). Occasionally, I will pop into my local supermarket (like Tesco Express but not that) and use a £10 note for something £1 at a self service machine to get £9 change. I've started to wonder if I can get in trouble for this is I do it often? Or am I entitled/allowed to do this as regularly as I want? Genuinely don't know if IABU.