Late payment interest calculator for overdue invoices in Morocco

How does the estimator calculate late payment interest?

It follows the simple interest formula: interest = unpaid amount × annual rate × days late ÷ (100 × 365), or ÷ (100 × 360) if your contract uses a 360-day year. Days late are the calendar days from the due date to the payment date, or to the calculation date if the invoice is still unpaid. An invoice paid on or before its due date has 0 days late, so no interest.

Interest is not compounded: it is calculated on the principal only, never on interest already accrued. The tool also shows the interest per day, so you can see what each extra day costs, and the total amount, meaning the principal plus interest. What people usually call late payment penalties is shown here as this interest, at the rate you enter.

Worked example: 10,000.00 MAD (DH) paid 99 days late

An invoice of 10,000.00 MAD (DH) falls due on 30 June 2026 and is only paid on 7 October 2026: that is 99 calendar days late. For the example, the user enters an annual rate of 10 %. This figure is purely an assumption for the calculation, not a legal rate and not a recommendation.

On a 365-day basis: 10,000.00 × 10 × 99 ÷ 36,500 = 271.23 MAD (DH) of interest, about 2.74 MAD (DH) for each day late, for a total of 10,271.23 MAD (DH). On a 360-day basis, the same calculation gives 275.00 MAD (DH). The difference comes only from the day-count basis, so always use the one written in the contract.

Which rate should you enter, and what about law 69-21?

The tool has no default rate, on purpose. Enter the rate in your contract, your general terms of sale or your invoice, or the one your expert-comptable (chartered accountant) or lawyer has confirmed. A rate picked at random gives a meaningless result.

In Morocco, payment terms between businesses fall under the framework of law 69-21. The rules, rates and procedure that apply depend on your situation and on the texts in force, which can change. Before claiming interest from a customer, have the applicable rate and the procedure validated by an expert-comptable or a lawyer.

The result is an indicative estimate: it quantifies interest, but does not say whether it is owed or how to claim it.

Common mistakes when calculating late payment penalties

Most differences between two calculations come from a few simple mistakes.

• Counting from the invoice date instead of the due date.
• Mixing the 360-day and 365-day bases from one calculation or customer to another.
• Compounding interest when the contract provides for simple interest.
• Issuing an invoice with no written payment terms or due date, which makes the start of the delay debatable.
• Keeping no written record of the reminders sent to the customer.
• Confusing late interest with other charges, such as bank fees on an unpaid bill of exchange or an indemnity set in the contract, which follow their own rules.

How SOGESTIO helps you track due dates and late payments

The best way to limit the interest you have to chase is to spot late payments early. In SOGESTIO, every invoice carries payment terms (cash, 7, 15, 30, 45, 60 or 90 days, or custom) with an automatically calculated due date, and payments are recorded as they come in.

The dashboard shows customer receivables, unpaid invoices and late payments, reports give your average payment delay (DSO), and the 13-week cash-flow forecast shows how delays affect incoming cash. Cheques and bills of exchange (LCN) are tracked with their due date and status, a credit limit can be set per customer, and the client portal lets each customer view their invoices and download the PDFs.