saffynabster:
they normally charge the intrest on a set day of the month for example mine is last day ov month so in theory as long as u put some money back in before they charge it you will be okay.thats how mine works anyway.
the intest is usually a percentage ov what your overdrawn my intrest is 1.45% so on a 100quid overdraft they charge me about £1.50ish a month.
Thats okay but the OP was concerned about going over, this would cause a charge to be put on the account as soon as that occurs, interest will be paid on any overdraft for as long as it is overdrawn and usually on a day by day basis