I believe it is possible to claim zero allowances and still owe income tax. When the tax law changes were implemented last year the withholding tables were reduced to accommodate the reduction of tax rates, so it is possible that tax withholding was reduced enough to create a balance due even if zero exemptions were claimed. To avoid this situation in the future, taxpayers can request employers to withhold additional amounts over and above the amounts indicated on the tax withholding tables.
