Cash flow / Free financial tools

Late Payment Interest & Penalty Estimator

Model a balance using entered interest and penalty assumptions, with simple or daily-compound interest.

USD • Custom rates · Instant results · No sign-up

Enable JavaScript to use this interactive calculator. The calculation method and assumptions are explained below.

How this calculator works

Simple interest = balance × annual rate × days ÷ day basis. Daily compound interest uses balance × [(1 + rate/day basis)^days − 1]. The optional penalty uses the entered monthly rate, cap and fixed amount.

Planning estimate only. Review the assumptions alongside the result before using it for a tax, financing or business decision.

Common questions

Does this calculate my IRS notice?

No. IRS rates change by quarter and specific penalties have different bases, caps and interactions. Use the notice and applicable guidance to establish inputs.

What if my balance changed?

Calculate each balance/rate segment separately. This single-period model assumes a constant balance and rate.

Put your numbers into context.

A calculator can help you ask better questions. Tell ZTax what you are planning and we will discuss the records, scope and support you need.

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