I paid my sales tax late. Which return do I put it on? 2016 or do I wait til I file my 2017 tax return since I paid it in 2017?

I missed the last due date to pay sales tax in 2016 and paid it and the fees recently in 2017.  I am confused as to which tax return I put it on since it was sales tax for 2016, but I paid it in 2017.  I edit manuscripts in PA as an independent contractor and run my business online.