install TurboTax on multiple PC with additional state return?

Dear All,

 

I'm planning to buy TurboTax desktop version for the first time, but I want to know the answer before I buy it. If I want to install TT on different PCs with additional state return, should I need to purchase the additional state return separately for each PC, or I only need one purchase for the additional state on one PC and it can automatically show up on other PCs? Thank you.