Did she only have a small amount of income from the employer? Does the withholding on her W-2 match what her company showed on her earning statement? If the statement shows no withholding and if she had substantial income, the employer may have made a mistake in withholding during the year. Didn't she notice during the year that nothing was being withheld? You have no choice but to pay the tax out of pocket now since she received all that extra take home pay during the year.