You open your mail in October and there’s a notice from the IRS. Underpayment penalty. You owe an extra $800 on top of your regular tax bill because you didn’t make quarterly estimated payments. Or you made them but calculated wrong. This happens to NJ business owners constantly. You’re focused on landing clients, managing cash flow, hiring people, and keeping the business running. Quarterly tax estimates feel like busy work until the penalties show up.…