"You had ABP interest adjustment (Schedule B), you need to upgrade to Deluxe version to file" [removed] I don't have any bond. My interest income is only $350.

[ToddL]

You may have an ABP interest adjustment and not know it, or the program thinks you have one even though you don't (see below for an explanation).

In either case, you can avoid the upgrade by using "Delete a Form" tool (as described below).  If the amount is small (e.g. < $10) this will not change your tax return in any material way.

"ABP" is an amortized bond premium. This means you purchased a bond at a certain price above  par. For example, you paid  $1870 for an $1800 bond. 

Did you import your 1099-INTs or enter them manually? In either case, did you have an entry (even a $0) in Line 11 of either 1099-INT?

If you had a positive entry (>$0) on Line 11 of your 1099-INT, you will have an ABP interest adjustment. The TurboTax program will prompt you to upgrade if this adjustment cannot be calculated or reported using TurboTax Free Edition (Online). 

If you had a "$0" on Line 11 of your 1099-INT, you don't have an ABP interest adjustment, but the program thinks you do. You would have to delete the Form 1099 and re-enter it in the 1099-INT interview - any Lines with a "$0" amount should be left blank (i.e. don't type in a "0"). 

See our AnswerXchange article How do I delete forms in TurboTax Online?

[SS2]

The explanation is very helpful. You should also not choose the option to import your broker's information. I had to delete my entire return and start over. The second time through I entered the info manually and the program allowed me to continue using the free edition at the end. Otherwise the software forces you to pay for something you do not need. It's deceptive and dishonest.