By "online software that I downloaded" I'll assume that means you downloaded and installed the TurboTax Deluxe program and have been using it correctly, as opposed to logging into Online TurboTax version by mistake in a browser to prepare the return.
So if you are indeed using the desktop software installed on your computer, what exactly is it asking you to pay for? In the desktop products, the only additional fees would be a 19.99 state efile fee IF one is efiling a state return, or the purchase of an optional add-on such as Audit Defense.
The state efile fee wouldn't make sense, since the Deluxe 29.99 from Costco is a Federal-only product. It does not include a state program. So did you happen to buy Audit Defense?
When it asks you "how do you want to pay?" what is it telling you in your order that needs to be paid for?
