This probably should be common sense, but just a reminder: don’t pay your taxes with your credit card.

Although a lot of credit card companies offer rewards to customers who pay the IRS off with the imaginary money imbibed through the magic of an extravagant interest rate into a small piece of plastic in their wallets, the drawbacks can far outweigh the benefits.

For one, you’ll probably be adding as much as 2.9% to the tax that you need to pay, in addition to whatever your APR is. There’s also the risk that if you add it to an existing credit card balance, you might be forced to miss payments, which will give your credit card provider full license to up your APR to something mind-shatteringly exorbitant.

Hell, you guys know what you’re doing, but the warning here is that if you’ve got a big tax bill, pull out the trusty electro-abacus and do some math before you load it up on your Diner’s Club Card. Because knowing is half the battle.

Paying Taxes With Your Credit Card Can Get Expensive

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