Pay 0% interest on purchases and balance transfers for 18 months when you sign up for the Citi Simplicity MasterCard. If you are paying off a credit card debt or making a big ticket purchase, this card can save you a considerable amount of interest. While there's no annual fee, balance transfers attract a fee of 3%. That's the standard rate for this kind of offer. Annualized over 18 months, the 3% fee at 0% interest works out to around 2%, which is a big difference from normal credit card rates.