One interest day
Payment one day after the due date produces an estimated C$1.92 of interest at 7% ÷ 365.
Free · private · verified quarters only
GST/HST arrears-interest calculator.
Estimate daily-compounded CRA arrears interest on one unchanged overdue GST/HST balance. The calculator covers July 1, 2025 through September 30, 2026, uses the published 7% rate for each included quarter, and stops when account activity would make a simple estimate unreliable.
Transparent calculation
How the narrow daily-compounding estimate works.
Section 79.03 of the Excise Tax Act says interest is compounded daily from the first day after payment was required through the day it is paid. CRA publishes the annual GST/HST overdue rate each quarter; every supported quarter is 7%.
| Step | Rule used | Calculator treatment |
|---|---|---|
| Principal | One overdue GST/HST amount | The entered principal stays unchanged |
| Interest period | Day after the due date through payment day | Both the first interest day and payment day are counted |
| Daily rate | Annual prescribed rate ÷ days in the year | 7% ÷ 365 in the supported 2025–2026 window |
| Compounding | Interest is added daily | Each next day starts with the prior day’s balance |
| Estimate | Compounded balance less principal | Rounded to cents after the full calculation |
Published rate window
The five GST/HST quarters this version can verify.
The rate is determined every three months. This version deliberately ends on September 30, 2026 instead of guessing a future quarter.
| Calendar quarter | Dates included | GST/HST overdue rate |
|---|---|---|
| 2025 Q3 | July 1–September 30, 2025 | 7% |
| 2025 Q4 | October 1–December 31, 2025 | 7% |
| 2026 Q1 | January 1–March 31, 2026 | 7% |
| 2026 Q2 | April 1–June 30, 2026 | 7% |
| 2026 Q3 | July 1–September 30, 2026 | 7% |
Cent checks
Three examples on an unchanged C$10,000 balance.
Thirty-one interest days
Daily compounding for 31 days produces an estimated C$59.62, not a simple monthly percentage.
Three hundred sixty-five days
Daily compounding for 365 days produces an estimated C$725.01. The effective annual amount is slightly above 7% because interest compounds.
Use account facts
Estimate first, then confirm the live CRA balance.
- 01
Copy the final GST/HST payment due date and overdue principal from the CRA account or assessment.
- 02
Confirm that no partial payment, credit, penalty, relief, waiver, refund, transfer, or other account transaction changed the balance during the period.
- 03
Enter the actual payment date, or a planned date no later than September 30, 2026, and review every quarter used.
- 04
Before paying, use Calculate future balance in the CRA account because CRA controls the assessed balance, transaction allocation, and rounding.
Primary sources
Verify the period, rate, law, and relief boundary.
The estimator is intentionally narrower than a CRA account. These official pages establish daily compounding, the included quarterly rate, the statutory start and end days, and why pre-July 2025 balances need different treatment.
Canada Revenue AgencyGST/HST arrears interest and Calculate future balanceOpen the current official source Canada Revenue AgencyPrescribed interest-rate quarter indexOpen the current official source Canada Revenue Agency2026 Q3 GST/HST overdue rate: 7%Open the current official source Justice LawsExcise Tax Act, section 79.03Open the current official source Canada Revenue Agency2025 tariff-relief period and July 1 restartOpen the current official source
Interest questions
Know when the estimate is useful—and when to stop.
How does CRA calculate GST/HST arrears interest?
CRA says the prescribed rate is determined every three months and arrears interest is compounded daily. Section 79.03 starts the period on the first day after payment was required and ends it on the payment day.
Is the payment day included?
Yes. The statutory period ends on the day the amount is paid. A payment one day after the due date therefore has one interest day in this estimate.
Why does the calculator begin with a June 30, 2025 due date?
CRA automatically provided GST/HST interest relief through June 30, 2025 in response to tariffs and says interest resumed July 1. The minimum due date keeps every estimated interest day after that exceptional relief period.
Why does it stop at September 30, 2026?
Prescribed rates are published quarterly. September 30, 2026 is the last day of the newest published quarter included in this version, so the tool does not guess a future rate.
Can I use it after a partial payment or credit?
No. A partial payment, credit, refund, transfer, penalty, relief decision, or other account transaction changes the daily principal. Use CRA’s live account calculation instead.
Does it include a late-filing penalty or instalment interest?
No. Late-filing penalties and instalment interest follow separate rules. The linked penalty calculator estimates only the ordinary filing formula; CRA remains the source for an actual account balance.
Does it calculate Québec QST interest?
No. This is a federal GST/HST arrears-interest estimate for amounts payable to CRA. It does not calculate QST, Revenu Québec account interest, or combined federal and Québec balances.
Is this the exact amount I should pay?
No. It is a planning estimate for a narrow unchanged-balance case. Use Calculate future balance in the CRA account immediately before payment and follow any assessment or arrangement that applies to the account.
Educational scope
Prepare a review questionA planning estimate is not a CRA account balance.
The tool does not determine whether an amount is legally owing, the correct due date, payment allocation, penalties, instalment or refund interest, partial payments, credits, transfers, reassessments, tariff relief, taxpayer relief, waivers, payment arrangements, collections, objections, QST, or future prescribed rates. It does not access an account, make a payment, or contact CRA.
Public resource
Share the bounded interest calculator.
Send the bilingual public page to a registrant who needs a transparent estimate and a clear reason to verify the final amount in the CRA account.