You finally get down to the bottom line of your tax return, and the balance due to Uncle Sam is much more than you expected. In fact, it's more than you can afford to pay. You've dug through the couch cushions and checked all your pants pockets, but all you got was $26.55 and a lot of lint.

What now?

Pay what you can to avoid the IRS's ire
Don't let your inability to pay your tax liability in full keep you from filing your tax return properly and on time. Include as large a partial payment as you can. Too many taxpayers hide their heads in the sand when they run into financial difficulties. But tax liabilities don't go away when ignored. In fact, they get worse.

If you don't cooperate with the IRS, you can expect escalating penalties, plus the risk of having liens assessed against your assets and your income. Down the road, the collection process could also include the seizure and sale of your property. In many cases, these tax nightmares can be avoided by taking advantage of arrangements readily offered by the IRS.

The simple act of filing your return, even if you don't include full payment, can save you substantial amounts in late-filing penalties. You can also keep the IRS from instituting its collection process with some payment extension procedures and installment-payment arrangements.

5 solutions when you're short on cash
So after you've paid what you can, what's next? Here are five possible solutions.

1. Pay late: If your inability to pay the taxes you owe is simply a short-term cash-flow problem, and you'll have the funds to make the payment in a few weeks or months, the solution is simple. Pay as much as you can when you file your tax return. As mentioned before, that payment will help reduce the penalties and interest you'll be charged.

In about 45 days, the IRS will send you a bill for the remaining balance due. If you can pay it then, do so. If you can't, send as much as possible (again, reducing penalties and interest) and hang on. In another 45 days or so you'll get another bill from Uncle Sam. With any luck, you can then pay the balance due.

You'll likely be able to go through two or three of these billing cycles before the IRS bugs you for some type of formal payment method. But if you can clear up the matter using bigger chunks of payments over two or three IRS billing cycles, you'll pay some interest and penalties, but you'll save some time by not being required to complete additional IRS paperwork.

2. Borrow the money: Try to put the bite on your friends or family -- seriously. If you can pay the entire amount with borrowed funds, you'll reduce the penalties and interest you'll owe Uncle Sam. And I'm sure you'll find making repayments to friends and/or relatives a much more pleasant experience than making payments to the folks at the IRS. If friends or family can't help, consider a bank loan. Again, paying your friendly banker may be more pleasant than haggling with Uncle Sam.

3. Pay by credit card: As an alternative to paying by check, the IRS (and many states) will gladly accept payment by credit card. We generally don't recommend credit card payments, because the fees and interest rates associated with this type of payment are often high. But sometimes, you gotta do what you gotta do.

4. Enter into an installment agreement: If you're still reading, it's possible that none of the above solutions work for you. If so, consider a formal installment agreement with the IRS. Be aware that you'll be dealing with the IRS directly, which may require some additional forms and paperwork.

Generally, the IRS will accept an installment agreement if the tax owed is less than $25,000 and the balance due will be paid within five years. Additionally, if your balance due is $10,000 or less, and you meet some other guidelines, the IRS can't deny your request. You'll be required to pay a "user fee" of $105 (or $52 if you use electronic funds withdrawal) to obtain the installment agreement, and you'll still get hit with monthly late-payment penalties of 0.25%. But an installment agreement is still better than ignoring your obligation.

If you think an installment agreement is for you, make your request on IRS Form 9465 -- Installment Agreement Request (link opens a PDF). You can file this form separately, or you can simply attach the form to your tax return, which should be filed by the normal April 15 deadline.

5. Request an extension to pay: If all else fails, you can request a six-month extension of time to pay your taxes. But this extension will be granted only if the payment will cause undue hardship on you or your family. Don't confuse the term "undue hardship" with "inconvenience." You'll have to prove that you can't sell assets and/or borrow to pay your taxes, except under terms that would cause severe loss and undue hardship.

As with the installment agreement, you'll be required to file additional documents. You'll have to provide statements of assets, liabilities, income, and expenses for three months preceding the filing due date. You can use IRS Form 1127 (link opens a PDF) if you think you qualify for an extension of time to pay your taxes. But be warned: Form 1127 must be filed by the due date of the tax return, and it's not the best way to go. Heck, even the form warns you against using it. Even if you do qualify for an extension to pay, you'll still be charged interest on the balance due.

Dig deep and pay up
It's no fun to pay your taxes. But if you find yourself with a tax balance due and an empty checkbook, don't just throw your hands up. Do the right thing -- or at least do something. You'll save yourself substantial penalties and interest payments by addressing the issue head-on.

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This article, written by Roy Lewis, was originally published on April 17, 2007. It has been updated by Dayana Yochim. The Fool has a disclosure policy.