If you plan to pay your taxes by credit card because you're short of cash now, the government offers an option that can cost far less. The IRS automatically accepts requests for payment installment plans (also called installment agreements) for up to $50,000 in combined taxes, penalties and interest. You'll pay interest as long as you owe, but the IRS's interest rate--3 percent for the first quarter of 2012--is far less than the average credit-card rate, and isn't likely to jump up sharply over time like a credit-card teaser rate. (If you choose the installment plan, you still have to file the return on time on April 17 to avoid penalties; you just don't have to pay everything then.)
You can apply for an installment agreement here. To set up such an agreement, you will have to pay a fee that ranges from $43 to $105, depending on the arrangement and your income level.
If you still want to pay taxes by credit card to earn loyalty rewards, read why we think that's not such a wise idea.