IRS Form W-4 showing how employees adjust tax withholding, used to illustrate the impact of withholding errors on IRS underpayment penalties.

Last month, I met with a woman who thought she was “taken care of” when it came to her taxes. She had a CPA, a solid income, and a W-4 on file she hadn’t touched in years. But when tax season rolled around, the IRS disagreed. She ended up paying