The estimated tax safe harbor demands 110% of last year’s tax for AGI over $150,000 — pay that and no underpayment penalty hits, no matter how big the final tax
A taxpayer whose 2025 return showed $80,000 in total federal tax can make the IRS underpayment penalty vanish for 2026 by doing one thing: paying at least $88,000 through withholding and estimated payments over the course of the year. If the actual 2026 tax bill lands at $200,000, the $112,000 shortfall triggers no penalty at…