A prepayment code isn't required. You can choose to pay by credit card if you prefer by clicking the Continue button below the prepayment box. If you don't see a Continue button, you can either zoom out to make your screen smaller or save/log out and then log back into TurboTax.
You have clicked a link to a site outside of the TurboTax Community. By clicking "Continue", you will leave the Community and be taken to that site instead.