[Editor's Note: This article was originally published in February 2014 but has been updated for accuracy and comprehensiveness.]
How can I use my W-4 form to increase my paycheck or avoid tax debt?
If your tax refund was lower than expected (or you ended up owing the IRS) you may not be withholding the right amount of federal tax from your paycheck. On the other hand, if your refund was unusually large, you could be having too much tax withheld, reducing your take-home pay throughout the year.

