Are you using TurboTax CD/Download or TurboTax Online?

Where do I enter income on T5 Box13 Bank interest

Use the search on the Tax Home page to look for "T5".

box 13 defaults to bank interest can't enter the amount. Why?

@Tracita If you see a lock next to a box, you can enter an amount, but you'll be required to upgrade the version of TurboTax Online that you are using.