What is the convenience fee for paying taxes with a credit card?

A Convenience fee of 2.49% of the total amount you owe will be charged by our credit card service provider.  There is a minimum convenience fee of $3.95 regardless of of your IRS payment obligation.

If you want to pay the federal taxes owed with a credit card, the fee are lower if you use one of the IRS approved credit card payment providers on this IRS website - https://www.irs.gov/payments/pay-your-taxes-by-debit-or-credit-card

While TurboTax does not charge you to use your credit card, as per @DoninGA  there is a convenience fee, which is charged by the payment processor.  If you owe the IRS and you're e-filing, select the option Charge my credit card when asked how you want to pay your federal taxes in the File section to do so.

You can use a direct debit, which is free, instead of paying the convenience fee for debit card payment.

The three providers — PayUSAtax, Pay1040, and ACI Payments, Inc. — charge a fee. These fees are often between $2 and $4. The fee is based upon a percentage of the payment amount. The IRS accepts Visa, Discover, American Express, Mastercard, STAR, Pulse, NYCE, Accel, PayPal, and PayNearMe.

In addition, you can also  use your federal refund to pay your TurboTax fees.  There’s a $40 processing fee charged by the bank that handles the transaction when the IRS processes your return. If your return is rejected, you might have to enter your bank account information again, but you won’t be charged a second time.

Click here for "Can I pay with My Refund?"
Click here for information on "How to Pay Your Taxes."

Please feel free to come back to TurboTax Community with additional information or questions or click here for help in contacting Turbo Tax Support. 

To pay the tax due with another one of the IRS  credit card providers just say you will mail a check.  Then pay directly online at the IRS either with a credit card or direct debit from your bank account.