It sounds like you may have chosen to pay your Federal taxes with a credit card, in which case the screen does mention a service fee when using a credit card.
https://ttlc.intuit.com/questions/2580013-can-i-pay-my-irs-taxes-with-a-credit-or-debit-card
The IRS also charges a fee when paying taxes due with a credit card.
https://www.irs.gov/payments/pay-taxes-by-credit-or-debit-card
