I have a personal credit card 0% on purchases, I put my monthly personal expenses on and pay off, mainly for the bonuses/points for doing this.
I had incurred about £2000 of expenses attached to a community project I am involved in so decided to balance transfer them to a 0% balance transfer card until I can claim them back. Keeps things tidier. All fine until I accidentally paid my annual car insurance on the balance transfer card, not an issue in that that card also had 0% on purchases for 3 months, if I pay off the purchase on that card before the end of the 3 months, will I get charged interest on the balance transfer amount because I've also used it for purchases? ie how would they know if I pay £300 off that that was the car insurance not the balance transfer I was paying?