Penalties, Refund & Rate Tools

IRS penalty math (underpayment, late filing/payment with interest), plus refund estimator and marginal vs effective rate analysis.

Total tax owed (current year)

Total paid (withholding + estimates)

Prior-year total tax

AGI

Above $150k triggers 110% safe harbor.

Safe harbor required

$13,200

Shortfall

$5,200

Estimated penalty (~8%)

$416

Penalty math uses the current ~8% IRS underpayment rate; statutory caps and interest compounding may differ slightly. Always confirm with Form 2210/1040.