Introduction

Many incorporated business owners are aware that personal taxes can require instalment payments — but the instalment obligations for corporations operate differently and on a separate schedule. For a growing corporation whose tax owing has crossed certain thresholds, understanding the instalment system is part of basic compliance.

What Are Corporate Tax Instalments?

Corporate tax instalments are periodic prepayments of estimated corporate income tax, made throughout the taxation year, rather than as a single lump sum after the year ends. The purpose is to bring the collection of tax closer to the period in which the income is earned — rather than allowing corporations to defer payment until the filing deadline.

Which Corporations Must Pay Instalments?

A corporation is required to pay instalments if its combined federal and provincial tax payable (net of refundable tax credits) for either the current year or the previous year exceeds $3,000. For most profitable corporations, this threshold is crossed relatively early.

A corporation in its first year of operation is generally not required to pay instalments. A corporation with consistently high tax owing in prior years will be making monthly instalments throughout the year.

Instalment Frequency

For most corporations — CCPCs with taxable income below the SBD limit and with good compliance histories — the instalment frequency is monthly. Instalments are due on the last day of each month of the taxation year following the first taxation month.

For CCPCs that qualify (based on prior year tax owing and SBD eligibility), quarterly instalments are permitted. Quarterly instalments are due on the last day of the third, sixth, ninth, and twelfth months of the taxation year.

The CRA assigns the instalment frequency based on the corporation's history. A corporation that wants to confirm its required frequency should review its CRA My Business Account or consult with its CPA.

How to Calculate Instalment Amounts

There are three methods for calculating instalment amounts, and a corporation can use whichever results in the lowest instalments without penalty:

Method 1 — Prior year tax: Pay one-twelfth (monthly) or one-quarter (quarterly) of the prior year's net tax owing.

Method 2 — Second prior year and current year: For the first two instalments (or first quarter), use the second prior year's tax as the base. For subsequent instalments, use the current year's estimated tax.

Method 3 — Current year estimate: Base instalments on the current year's estimated tax. If the estimate is accurate, this method produces instalments that exactly match the liability — but underpayment interest applies if the estimate is too low.

For most corporations, Method 1 (based on prior year tax) is the simplest and most predictable. It does not require estimating current-year income and provides protection against underpayment interest as long as the instalments equal the prior year's tax.

The Instalment Interest Calculation

If a corporation pays less than required in any instalment period, the CRA charges instalment interest on the shortfall. Interest is calculated from the date the instalment was due to the date the tax is ultimately paid.

Importantly, instalment interest is offset by instalment overpayments in some periods. The CRA's calculation considers the full pattern of instalment payments across the year, not each payment in isolation. A corporation that overpays in some months and underpays in others may still incur net instalment interest depending on the timing.

There is no penalty for underpaid instalments — only interest. However, a corporation that consistently underpays instalments and also underpays the final balance may face interest charges that accumulate across multiple periods.

The Final Balance Due Date

The final balance of corporate tax — the amount owing after deducting all instalments paid — is due two months after the end of the fiscal year for most corporations, or three months after the end of the fiscal year for CCPCs that claim the small business deduction and meet certain other conditions.

The T2 return itself is not due until six months after the fiscal year end — but the tax payment is due earlier. A corporation that waits to pay its tax balance until the T2 is filed may be paying late and incurring interest on the outstanding balance.

When to Speak With a CPA

For a corporation approaching its year end with significant estimated income, reviewing the instalment position before the year closes — and the final balance due date after it closes — can prevent unnecessary interest costs. A CPA can model the instalment obligation and ensure payments are structured to minimise interest.

Rotaru CPA helps incorporated businesses manage their CRA instalment obligations and avoid unnecessary interest charges. Book a consultation to review your corporation's instalment position.