So have you already done the upgrade part to PLUS? If you have already upgraded the 2018 return to PLUS, I can tell you below how to pay for it (19.99) by credit/debit card with straightforward steps. Whatever you do, don't upgrade any farther, or you'll have problems.
The 2017 and 2018 returns must be in the same account.
- With the 2018 return open, if you have already upgraded to PLUS, then go to the left menu column and click on TAX TOOLS, then PRINT CENTER.
- At the Print Center choose to "Print, save, view THIS YEAR's return." (Yes, you say "this year's" because you are paying for the 2018 return to unlock the 2017 return.) You don't actually have to print it.
- It will ask you to pay. If the Order Summary appears OK, then choose PAY NOW.
- You can pay by credit card or debit card (even though it only says "credit.")
NOTE: If it should offer you the choice of paying later out of the Federal refund, that cannot be done for this purpose. You have to choose PAY NOW.