If I understand you correctly, you claimed zero allowances on your W-4, yet you still owe tax.
The W-4 is only a crude estimate of how much tax needs to be withheld from your paycheck. For people who earn income in addition to their W-2, who have more than one W-2, who earn bonuses or commissions or who have a spouse that earns income, the estimate can be way off.
Your best solution for next year is to file a new W-4 with your employer and request that additional tax be withheld on Line 6 of that form. To make sure that you don't owe tax next year,
- Estimate next year's income and divide by this year's.
- Multiply the amount of tax you owe this year by the answer above.
- Divide the answer in step 2 by the number of pay periods remaining in the year and enter that number on Line 6 of the W-4.
Bear in mind that if you increase your withholding, you will decrease the size of your paycheck. Only you can decide the best answer.
