After April 30: The May and June Tax Deadlines Ontario Businesses Forget

What many business owners don't realize: April 30 is just one deadline in a series of tax obligations that run throughout the year.

April 30 arrives. You file your personal tax return. Tax season is over, right?

Not if you’re a business owner in Ontario.

April 30 is the deadline most people know about. It gets attention. Reminders. Media coverage. Everyone knows it’s coming.

What most Ontario business owners don’t realize: April 30 is just one deadline in a series of tax obligations that run throughout the year.

May brings deadlines. June brings deadlines. Some are for specific business structures. Others apply broadly. All have consequences if missed.

At KKCPA, late April and early May is when we see business owners asking: “Wait, what else do I need to file? I thought I was done after April 30.”

The problem isn’t that these deadlines don’t exist or aren’t important. The problem is that they don’t get the same attention as April 30, so business owners either don’t know about them or forget them until it’s too late.

Here’s what Ontario business owners need to know about the tax deadlines that come after April 30.

June 15: The Self-Employed Filing Extension (That Doesn’t Help With Payment)

If you’re self-employed or your spouse is self-employed, your filing deadline isn’t April 30—it’s June 15.

Who this applies to:

Sole proprietors, partnerships, anyone with self-employment income reported on a T1 return.

What the extension covers:

You have until June 15 to file your tax return without late-filing penalties.

What the extension doesn’t cover:

Payment. Any balance owing is still due April 30. If you don’t pay by April 30, you’re accruing interest from May 1 even though your filing deadline is June 15.

The confusion this creates:

Business owners hear “June 15 deadline” and think everything is due June 15. Then they’re surprised when CRA charges interest from May 1 on unpaid balances.

Why this matters:

If you owe $10,000 and don’t pay until June 15, you’re paying approximately 45 days of interest (May 1 to June 15) even though you filed on time.

At CRA’s prescribed interest rate (currently posted on their website), that’s roughly $150 in unnecessary interest just from misunderstanding the payment vs. filing distinction.

June 15: Quarterly Tax Instalments

Tax instalments are quarterly payments for individuals and corporations whose tax owing exceeds certain thresholds.

For individuals:

If you owed more than $3,000 in tax for the current year and either of the two previous years, you’re required to pay quarterly instalments.

Instalment due dates for individuals:

March 15, June 15, September 15, December 15.

For corporations:

Instalment requirements depend on prior-year and current-year tax amounts.

Why June 15 matters:

It’s the second instalment deadline of the year. If you missed March 15 (which many do because they’re focused on year-end filing), June 15 is your next payment date.

What happens if you miss instalments:

CRA charges instalment interest. This is separate from interest on your final balance owing. You can owe interest for late instalments even if you have no balance owing when you file.

The calculation problem:

Determining whether you owe instalments, calculating the correct amount, and tracking payment deadlines requires understanding CRA’s instalment rules.

Many business owners either don’t know they owe instalments or miscalculate the amounts, leading to underpayment and instalment interest charges.

June 30: Corporate Tax Returns (For December 31 Year-End)

Incorporated businesses don’t file on April 30. Corporate tax filing deadlines are tied to the corporation’s fiscal year-end.

For corporations with December 31 year-end:

T2 corporate tax return is due June 30 (six months after year-end).

The disconnect:

While everyone is focused on April 30 personal filing, corporations with December 31 year-ends have until June 30. But many business owners mentally group “tax season” with April and forget about their June 30 corporate deadline.

The payment deadline distinction:

Just like personal tax, corporate filing deadline and payment deadline aren’t always the same.

For Canadian-Controlled Private Corporations (CCPCs) eligible for the small business deduction, tax payment is generally due two months after year-end (February 28 for December 31 year-end).

For other corporations, payment is due when the return is filed (June 30).

The complexity:

If you’re incorporated, you need to know:

Your fiscal year-end
Your filing deadline (six months after year-end)
Your payment deadline (which depends on CCPC status and income levels)
Whether you owe corporate instalments

Many incorporated business owners file their personal returns in April and forget they still have corporate obligations in June.

End of May: GST/HST Filing and Payment (For Some Businesses)

GST/HST filing frequency depends on your annual revenue and your election.

Annual filers with December 31 year-end:

GST/HST return due June 30. Payment due June 30.

But some businesses are quarterly or monthly filers.

Quarterly filers:

Returns due one month after the end of each quarter.

For Q1 (January-March), the return and payment are due April 30.

For Q2 (April-June), the return and payment are due July 31.

Monthly filers:

Returns due one month after each reporting period.

Why May matters:

If you’re a monthly filer, you have returns due in May for your March and April reporting periods.

The tracking problem:

Business owners often don’t clearly track which GST/HST filing frequency applies to them. They miss filing dates because they’re not sure when their returns are due.

May Through June: Payroll Remittances

If you have employees, you’re required to remit payroll deductions (income tax, CPP, EI) to CRA.

Remittance frequency depends on your average monthly withholding amount (AMWA):

Quarterly remitter: AMWA less than $1,000. Remittances due April 15, July 15, October 15, January 15.

Monthly remitter: AMWA $1,000-$24,999. Remittances due by the 15th of the following month.

Accelerated remitter: AMWA $25,000-$99,999. Remittances due twice monthly.

Threshold 1 accelerated remitter: AMWA $100,000+. Remittances due up to four times monthly.

Why May and June matter:

Monthly remitters have May 15 and June 15 deadlines for April and May payroll deductions.

The consequence of missing payroll remittances:

Penalties are significant. 3% if one to three days late, increasing to 20% for repeated failures.

CRA takes payroll remittances very seriously because you’re holding employee withholdings in trust for the government.

The complexity:

Knowing which remitter category you fall into, tracking payment dates, and ensuring amounts are correct requires understanding payroll rules that many business owners don’t have.

What Happens When You Miss These Deadlines

Missing May and June deadlines triggers the same penalties and interest as missing April 30.

Late-filing penalties: 5% of balance owing plus 1% per month late (up to 12 months). If you’ve been late before, penalties double.

Late payment: Compound daily interest on unpaid amounts from the due date.

Payroll remittance penalties: 3% to 20% depending on how late and how often.

Instalment interest: Charged on any deficiency from the due date.

If you miss multiple deadlines—June 15 instalment, June 30 corporate filing, May and June payroll remittances—the penalties and interest add up quickly.

The “I Didn’t Know It Applied to Me” Problem

One of the most common reasons business owners miss May and June deadlines: they don’t realize the deadlines apply to them.

Common scenarios:

“I’m incorporated so I filed by April 30″—your corporate return is due June 30.

“I paid what I owed in April”—you also owe June 15 instalments.

“I don’t remit GST/HST until year-end”—you’re actually a monthly or quarterly filer.

“Payroll deductions are handled by my payroll service”—your remittance responsibility remains.

Tax obligations are complex. Different deadlines apply to different business structures, revenue levels, and situations. Without comprehensive understanding of which obligations apply to you specifically, it’s easy to miss deadlines you don’t know exist.

Even if you use bookkeepers, payroll services, or accounting software, you’re ultimately responsible for meeting deadlines. If they miss a deadline, you face the penalties.

The Multiple Business Structure Problem

If you have multiple business structures, you face multiple deadline calendars.

Example: Self-employed with a corporation

Personal return (self-employment): Due June 15, payment due April 30. Corporate return: Due June 30. Personal instalments: March 15, June 15, September 15, December 15. Corporate instalments: Different schedule. GST/HST: Depends on filing frequency for each entity. Payroll: If you pay yourself or employees.

Each entity has its own calendar. Missing one doesn’t excuse missing others. Many business owners with multiple entities lose track of which deadlines apply to which entity and when.

The Cost of Discovering Missed Deadlines Later

You think you’ve met all your tax obligations. Months later, CRA sends a letter: you missed a deadline.

What this costs:

Penalties and interest from the missed deadline date. Professional fees to file late returns or remittances. Time dealing with CRA correspondence. Potential increased scrutiny if CRA sees a pattern.

Most missed May and June deadlines are avoidable if business owners know they exist and have systems to track them. The cost of properly tracking deadlines is far less than the cost of missing them repeatedly.

What a Complete Tax Calendar Actually Looks Like

For business owners, “tax season” isn’t April. It’s year-round obligations with multiple deadlines.

A sample calendar for an incorporated Ontario business owner with employees:

January: Corporate instalment (if required), payroll remittances

February: Corporate tax payment (if CCPC with December year-end), payroll remittances

March: Personal instalment, payroll remittances

April: Personal tax payment, Q1 GST/HST (if quarterly filer), payroll remittances

May: Payroll remittances

June: Personal filing (if self-employed), personal instalment, corporate filing (December year-end), payroll remittances

July: Q2 GST/HST, payroll remittances

August: Payroll remittances

September: Personal instalment, payroll remittances

October: Payroll remittances

November: Payroll remittances

December: Personal instalment, year-end planning, payroll remittances

The reality:

This isn’t an April problem. It’s an every-month problem.

Business owners who think tax obligations end on April 30 are missing roughly 80% of their compliance calendar.

The Bottom Line

April 30 gets all the attention. But for Ontario business owners, it’s just one deadline among many.

May and June bring corporate filing deadlines, instalment deadlines, GST/HST obligations, and ongoing payroll remittances.

Missing these deadlines costs the same as missing April 30: penalties, interest, CRA scrutiny.

The difference is that these deadlines don’t get media coverage or widespread reminders. Business owners either need to track them themselves or work with professionals who ensure nothing falls through the cracks.

And the most expensive mistake isn’t missing a deadline once. It’s not having systems in place to track all your obligations throughout the year, leading to repeated missed deadlines and escalating penalties.

Need Help Tracking Your Post-April 30 Tax Obligations?

At KKCPA, we help Ontario business owners identify which tax deadlines apply to them and ensure nothing gets missed.

We can help you:

Identify all tax filing, payment, and remittance obligations for your specific business structure
Create a complete tax calendar showing what’s due when throughout the year
Ensure corporate returns, instalments, GST/HST, and payroll obligations are tracked and met
Set up systems and reminders so deadlines don’t surprise you
Handle filings and payments on your behalf where appropriate

Don’t assume tax obligations end on April 30—or that what you don’t know won’t cost you.

Contact KKCPA |

📍 Serving Ontario businesses including Hamilton, Ancaster, Burlington, and the Greater Toronto Area
📞 Toll Free: 855-667-1727

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