In response to a letter from Senator Amy Klobuchar (D-MN), the Internal Revenue Service (IRS) recently released Information Letter 2010-0144, which includes a response to her constituent about the effect of the Making Work Pay tax credit on his employees’ annual withholding for 2009. The constituent was concerned that the reduced withholding would either reduce his employees’ refunds or increase the tax they would owe when they filed their 2009 and 2010 income tax returns. The IRS recommended that concerned employees consult the IRS withholding calculator and submit a revised Form W-4, Employee’s Withholding Allowance Certificate or its Spanish equivalent, Formulario W-4(SP), Certificado de Exención de la Retención del Empleado. Additionally, they should consult Publication 919, How Do I Adjust My Tax Withholding? Vision Payroll recommends that employees regularly review their income tax withholding to ensure the proper amount is paid in so that underpayment penalties may be avoided.