I paid my taxes yesterday through turbo tax using my credit card. In addition to the IRS payment and turbo tax cost there is a 500 dollar processing is this a mistake

[Opus 17]

If you are seeing a "pending" charge on your credit card app or web site, wait for the transaction to finalize.  There might be reasons (depending on your bank and the CC processor where the taxes were paid) why they would put a larger "hold" on the card than the final amount.  If the final amount is not what you expect, you will have to call customer support. 

Also, there is a processing fee for credit card payments in addition to the tax.  The processing fee is up to 3% if you pay on the IRS web site. I don't know what the processing fees are if you use Turbotax.

https://www.irs.gov/payments/pay-your-taxes-by-debit-or-credit-card