Track approved amounts, retention, and overdue days. Compare simple and compound interest for contract payments. Present cleaner records for reviews, negotiations, and supporting documentation.
| Milestone | Contract Price | Complete % | Previous Paid | Retention % | Rate % | Due Date | Payment Date | Grace Days | Interest | Total Payable |
|---|---|---|---|---|---|---|---|---|---|---|
| Structural Stage | 120000.00 | 45 | 30000.00 | 10 | 12 | 2026-04-01 | 2026-04-25 | 5 | 134.86 | 21734.86 |
| Interior Stage | 85000.00 | 68 | 42000.00 | 5 | 9 | 2026-05-10 | 2026-05-30 | 3 | 59.70 | 12634.70 |
Approved Work Value = Contract Price × (Completion Percent ÷ 100)
Current Gross Due = Approved Work Value − Previously Paid Amount
Retention Withheld = Current Gross Due × (Retention Percent ÷ 100)
Net Amount Subject to Interest = Current Gross Due − Retention Withheld
Late Days = Payment Date − (Due Date + Grace Days)
Simple Interest = Net Due × Annual Rate × (Late Days ÷ Day Basis)
Compound Interest = Net Due × [(1 + r ÷ n)^(n × t) − 1]
Here, r is the annual rate, n is compound periods per year, and t is late days divided by the selected day basis.
A progress payment interest calculator helps parties manage delayed milestone payments. It fits construction, consulting, supply, and document-based service contracts. Many agreements tie invoices to approved work stages. When payment arrives late, interest may apply. This page estimates the overdue charge with a clean method.
Progress billing usually starts with the contract value. The next step is the percent completed for the current claim. Prior payments must also be considered. Retention can reduce the amount immediately payable. The calculator separates approved value, current gross due, withheld retention, and net due. This helps users see the true principal used for interest.
Due dates matter because interest does not always start on invoice day. Some contracts include grace days. Others start charging after a stated payment deadline. The tool uses the selected due date, payment date, and grace period to find late days. It then applies the annual rate across a 360-day or 365-day basis. Users can compare simple interest with compound methods.
This approach improves payment reviews and internal controls. Contract managers can document delayed receivables. Vendors can support claims with consistent numbers. Owners and general contractors can audit progress draws before approval. Legal teams can also use the output during negotiation, settlement review, or notice drafting.
A strong record should match the contract language. Check the payment clause, retention clause, cure periods, and default terms. Confirm whether interest applies to the net amount or another balance. Review whether compounding is allowed. Then compare the result with the invoice trail, certified completion status, and payment ledger.
Use the calculator as a working estimate, not a substitute for legal advice. Contract terms differ across projects and jurisdictions. Still, a clear interest model reduces confusion. It makes late payment exposure easier to explain. It also supports cleaner reporting, faster reconciliation, and better contract administration.
The example table below shows how a single progress claim can change after retention and interest. Small delays can create noticeable extra cost on larger contracts. That is why accurate dates, rates, and prior payment history matter. Better calculations lead to better notices, approvals, and cash flow planning.
Use it before sending reminders, demand letters, or payment review summaries.
It estimates interest on a delayed progress payment. It also shows approved value, current gross due, retention withheld, net amount subject to interest, late days, and total payable.
No. In most cases, interest should apply only to the unpaid amount tied to the current progress claim. This calculator uses the net due after previous payments and retention adjustments.
Retention is often withheld under the contract until a later stage. Because it may not be immediately payable, many users prefer to calculate interest on the current net due instead.
A 360-day basis treats the year as 360 days. A 365-day basis uses the calendar-style annual denominator. The correct basis depends on the contract wording or internal finance practice.
Late days begin after the due date plus any grace days you enter. If payment happens before that point, the calculator returns zero late days and zero interest.
Use compound interest only if the agreement, statute, or policy allows it. Many contracts use simple interest. Always compare the clause language before relying on compounded results.
Yes. It helps structure a claim review by showing how the principal and interest were derived. That can support notices, reconciliations, negotiations, or audit discussions.
No. It is a practical estimating tool. Contract rights, notice rules, and allowable interest methods vary by project and jurisdiction. Review the governing documents before using the result formally.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.