I wish to use my one State filing for myself and pay for the state fling ($19.99) for my son's State. How do I make that happen? Turbotax Deluxe with One State Return BK

You can file up to 5 returns on TT Deluxe with one free state download.  You can do your taxes, and then when it comes to your son's TR, start his return and TT will guide you to pay for his State, if it sees it is different than yours.  Or, if you do his first, it will ask if that is the one you want for free.  Either way, you get one State for free (and can use it for more than one person or family in the State) and when it comes time to download then next State, TT will ask you to pay for it.  You can use your own Intuit account to pay for it, even though it is his TR, and then just ask him to reimburse you, if you want.