Canadian invoice interestcalculator
Estimate simple interest using your unpaid balance, annual rate and days overdue. This tool does not determine whether a fee is enforceable or add it to an invoice. Free, no signup; only your original balance carries into invoice review when you choose to continue.
The starting $2,500 balance, 18% rate and 60 days are an example, not a recommended rate. No agreed rate? You can still copy a reminder for the original balance.
Enter a balance above $0 and a rate from 0 to 100 to see an estimate.
At the same balance and rate, another 30 days would add $36.99 in simple interest. This is a calculation, not permission to charge it.
Still waiting on your $2,500.00?
Start with one agreed, unpaid invoice. Add the invoice, review its details and message, then decide whether to approve follow-up. Nothing is sent from this calculator.
Free forever for your business. No RemitRight subscription or collection commission. Standard card processing fees apply to card payments. You can start invoice review as a guest; an account and payment setup are required before customer outreach.
Create a free demand letter insteadAn editable letter to send in your business’s name. No account or payment setup needed.
A polite overdue invoice reminder you can copy
Start with the original unpaid balance and ask for a payment date. This reminder uses your balance and days overdue, without adding the estimated interest. Replace the placeholders, confirm any payments received, and review it before sending.
Only the original balance carries into manual invoice entry when you continue. The interest estimate and reminder stay here. Nothing is sent to your customer. You can explore RemitRight as a guest, then review an invoice before starting customer outreach.
How this calculation works
Simple interest = unpaid principal × annual rate ÷ 100 × days ÷ 365. We use a fixed 365-day year, do not compound interest and round the displayed result to cents. With $2,500 outstanding at 18% for 60 days, the estimate is $73.97. Another 30 days adds $36.99, rather than one-twelfth of a year.
If the customer paid partway through, calculate each period separately using the balance outstanding in that period, then add the interest amounts. This tool does not calculate tax on fees, flat penalties, grace periods, court interest or an effective borrowing APR.
Can I charge this amount in Canada?
The result alone cannot answer that. Section 4 of the federal Interest Act generally requires an equivalent yearly rate in a written contract quoting interest for a period shorter than a year; otherwise recovery above 5% per year is restricted, subject to the provision’s exceptions. A monthly rate and a compounded effective annual rate are not interchangeable.
Do not rely on the old blanket “60% limit.” The general criminal interest threshold changed to 35% APR on January 1, 2025. Applicability, agreement dates, included charges and exemptions matter. Neither 35% nor this calculator’s input range is a recommended or automatically permitted invoice rate. Get advice on disputed or unusual charges.
Interest or a payment plan?
When the customer accepts the invoice but cannot pay at once, discuss a schedule before adding more charges. RemitRight’s optional plan fee is separate from this interest estimate. It is disclosed to the customer before checkout, not automatically added by this calculator.
Understand the three- and five-month plans · What to do when a customer won’t pay
Sources and scope
Updated September 10, 2026 by RemitRight. General information, not an assessment of your contract.
Charging interest is easy. Collecting it is the hard part.
RemitRight texts your customer, offers them an automatic payment plan, and sends the money straight to you. There is no RemitRight subscription or setup fee. Customers choosing a plan agree to 3% over three months or 5% over five months; recovery is not guaranteed.
Explore as a guest · No RemitRight subscription · See how it works