How does the amount of tax I owe relate to my withholding?

Employers are required to pull a certain amount of money out of your paycheck each pay period and send it to the IRS. If you are self-employed, you required to send in a “quarterly estimated tax payment” on April 15th, June 15th, September 15th, and January 15th each year which does the same thing. However, the amount of money withheld by your employer or sent in as your tax payment is not necessarily related to the tax you actually owe. Every April 15th, these two amounts are reconciled. While a “big tax refund” is nice, it means you have really been loaning money to Uncle Sam interest free all year. While nobody likes an April tax bill, savvy tax planners ensure they pay the IRS as little as possible until as late as possible without paying any penalties or interest. That does require a reasonable ability to forecast your tax bill along with discipline not to spend it on something else. Be sure you understand the Safe Harbor rules to ensure you don't owe any penalties or interest come April.