..and be careful about using the card for buying stuff if the interest free bit was for a balance transfer, as that will immediately break it up.
But otherwise its a no brainer to put the cash in the best savings possible. (but don't spend it
)
Yeah! you've got to be very careful, because if you buy anything on the interest free card, your monthly payments increase, but they go towards the interest free part of your balance. So as time goes on, the proportion of interest bearing to interest free balance rises, which means that you are getting more interest added each month.
The trick is keep the balance moving - when your 12 months is up, find another interest free offer, and shift the balance there. If you are a bad money manager (like me) this means that the old credit card is now available for you to run yourself into even more debt. If you are sensible, just close it.
By the way, here's a tip I got from my
bank manager (honestly): don't just "not use" the old card, cut it up, send it back and cancel the account. This means that you can apply to that same credit card company after a year if they come up with a good new offer. It seems that there aren't as many credit card companies as there are cards, so you will not be able to transfer a balance to a new card if it's managed by the same company as the card you are transferring from.