After submitting my vehicle registration in Iowa ($50), turbo tax a came back with an additional state refund of $30. However, my state refund remained the same.

[MichaelL1 · Accepted solution]

What happened is that for the State of Iowa, the vehicle registration is based on value and weight of the vehicle you drive.  Only the part of the registration based on the value is considered a deductible tax.

In your case, you were able to deduct $30 of the $50 vehicle registration, however due to your tax situation (possibly unable to itemize, or no state tax, or not enough of deduction to change the tax on the return) it resulted in no change in the overall State tax on the return.