T2125 Self-Employment: 12 Common Filing Mistakes Before the June 15 2026 Deadline

If you had any self-employment income in 2025 — freelance gigs, consulting, rideshare, delivery, Etsy, OnlyFans, Airbnb operated as a business, or a full sole proprietorship — you report it on Form T2125 (Statement of Business or Professional Activities) attached to your T1.

Self-employed Canadians get an extended filing deadline of June 15, 2026, but a critical catch trips up thousands every year: any balance owing is still due April 30, 2026. File late with no balance owing and the penalty is $0. File on time but pay late and CRA charges interest from May 1.

Here are the 12 T2125 mistakes that cost freelancers and sole proprietors the most money — in order of frequency.

1. Mixing Up the June 15 Filing Deadline With the April 30 Payment Deadline

The single most common self-employed mistake. CRA’s extended June 15 deadline applies only to the paperwork — not the tax bill. Interest starts accruing on any unpaid balance on May 1, 2026, whether or not you have actually filed.

What to do: Estimate your 2025 tax liability by late April and make a payment via CRA My Account or online banking (CRA as payee) before April 30 even if you plan to file closer to June 15. If you overpay, the balance is refunded when you file.

What it costs you: Current CRA arrears interest is ~8% annualized, compounded daily. A $5,000 balance carried from May 1 to June 15 costs roughly $50 in interest — small in isolation, but you also miss the benefits of the tax pre-payment for CRA’s instalment calculations for 2026.

2. Not Registering for GST/HST After Crossing the $30,000 Threshold

If your total taxable revenue from all sources exceeded $30,000 in any single calendar quarter or in the four most recent consecutive quarters, you are no longer a small supplier and must register for GST/HST — retroactively.

Check: Sum your 2025 gross revenue (not net profit). If you crossed $30,000 at any point in 2025, you should have registered within 29 days of that moment. Missing the registration means CRA can come after you for the GST/HST you should have charged customers (even though you did not actually collect it) — you owe it out of pocket.

What it costs you: On $40,000 of Ontario revenue where you did not register, the deemed HST owing is roughly $4,600 that you absorb yourself. The GST/HST calculator shows how much you should have charged.

3. Claiming 100% of a Vehicle as a Business Expense

CRA flags this aggressively. Unless you have a second personal vehicle and contemporaneous logbook evidence, claiming 100% of your vehicle for a sole proprietorship is a reassessment waiting to happen.

What to do: Keep a mileage logbook — either a paper one or an app like MileIQ. At minimum, note start and end odometer readings on Jan 1 and Dec 31, plus a 12-week representative sample of business-vs-personal trips. CRA accepts a 12-week sample logbook as a proxy for a full year if you also record odometer readings at year-start and year-end.

What it costs you: A typical CRA reassessment of an over-claimed vehicle expense reduces the business portion from 100% to 30–60% and charges arrears interest on the resulting tax difference.

4. Forgetting the 50% Rule on Meals and Entertainment

Business meals and entertainment expenses are only 50% deductible — not 100%. This applies to taking clients to dinner, business lunches, sports tickets, and most conference meal expenses (exceptions: employee holiday parties up to $150/person, meals on remote work sites > 30 km from municipal centres, and a few long-haul trucker scenarios).

What to do: Keep meal receipts separate in your bookkeeping so you can apply the 50% limit at year-end. Do not apply 100% and hope CRA does not notice — line 8523 on the T2125 specifically caps at 50%.

What it costs you: Over-claiming $4,000 of meals at 100% instead of 50% inflates deductions by $2,000 — about $600 in tax at a 30% marginal rate, which becomes the reassessment amount plus interest.

5. Mishandling Business-Use-of-Home Expenses

Home office for a sole proprietor (T2125 Part 7 — Calculation of business-use-of-home expenses) is calculated very differently from an employee’s T2200 claim.

Key rules:

You must use the space regularly and continuously for business, OR use it exclusively for meeting clients
The deduction is limited to your business net income — it cannot create a loss
Unused amounts carry forward indefinitely to future years
Eligible expenses: mortgage interest (not principal), rent, property taxes, utilities, home insurance, minor repairs — allocated by square footage

What to do: Measure your office area and your total home area. Allocate proportionally. Do not include principal mortgage payments (common error — only interest is deductible) and do not claim 100% of internet or phone unless you have separate business lines.

What it costs you: Over-claiming home office tends to be flagged during audit because the percentages look suspicious. Under-claiming is just leaving money on the table — a freelancer working from a 200 sq ft office in a 1,200 sq ft apartment paying $24,000/year in rent and utilities can legitimately deduct ~$4,000.

6. Missing Capital Cost Allowance (CCA) on Equipment

Business equipment over $500 — laptop, camera, tools, vehicle, office furniture — is generally capital property that depreciates via Capital Cost Allowance rather than being expensed in full in the year of purchase.

Check: For 2025, the Accelerated Investment Incentive is in its phase-out period. Most Class 8 equipment (furniture, computers, tools) acquired in 2025 can claim 50% CCA in the first year instead of the normal half-year rule — a big acceleration. Class 10 (vehicles) follows separate rules with a cap.

What to do: List each capital asset on Area A of T2125 Part 4 with its class, cost, and prior-year balances. Claim CCA at the class rate. Remember CCA is optional each year — skipping it in a loss year preserves the pool for future use.

What it costs you: Expensing a $3,000 laptop as a supplies expense instead of capitalizing it typically triggers a CRA reassessment that reclassifies the expense, recovers the excess deduction, and charges interest.

7. Not Tracking Inventory Properly

If your business sells physical goods — handmade crafts, resold items, imported products — you owe CRA a cost of goods sold calculation, which requires inventory counts at year-start and year-end.

COGS formula: Opening inventory + Purchases during the year − Closing inventory = COGS.

What to do: Count inventory on December 31 at cost (lower of cost or fair market value). If you did not do this, estimate backwards from your sales records and last purchase invoices.

What it costs you: Misreporting COGS by $5,000 in either direction translates to a $1,500 tax difference at a 30% marginal rate — and inventory errors compound across years.

8. Claiming Personal Cell Phone at 100%

A cell phone used for both business and personal purposes must be allocated — not claimed at 100%. CRA typically accepts 60–80% business use as reasonable for a sole proprietor whose phone is their primary business contact; 100% is only defensible with a second personal phone.

What to do: Set a reasonable business-use percentage and stick with it consistently year after year. Keep one bill as documentation. Apply the same percentage to internet if it is shared.

What it costs you: Over-claiming by 30% on a $1,500/year phone + internet bundle costs you roughly $135 in tax — small, but this is exactly the category CRA scrapes for correspondence audits on freelancers.

9. Forgetting CPP Contributions on Self-Employment Income

Self-employed Canadians pay both sides of CPP (the employee portion and the employer portion) — 11.9% of net self-employment income above $3,500, up to the YMPE ceiling, plus CPP2 on earnings between YMPE and the CPP2 ceiling.

For 2025: YMPE is $71,300, CPP2 ceiling is $81,200. Maximum total CPP for a self-employed person in 2025 is approximately $8,885 (CPP1 + CPP2 combined).

Check: CPP is calculated on Schedule 8 of your T1, not on T2125 directly. Most tax software handles this automatically once T2125 net income is entered, but paper filers miss this step. You pay CPP on the same T1 balance owing, so underestimating April 30 payment without factoring in CPP leads to a surprise bill.

What it costs you: Forgetting CPP on a $50,000 net self-employment income means a surprise $5,400+ charge at filing time.

10. Failing to Make 2026 Tax Instalments

If your 2025 net tax owing (including CPP) exceeded $3,000 (federal + provincial combined) and also exceeded $3,000 in either 2023 or 2024, CRA will require quarterly instalment payments for 2026 starting March 15, 2026.

The instalment options:

Option 1 (CRA’s proposed amount): Pay what CRA says in their reminder
Option 2 (prior-year method): Pay 25% of your 2025 balance owing each quarter
Option 3 (current-year estimate): Pay 25% of what you expect to owe for 2026

If you meet any of the three, CRA does not charge instalment interest. If you skip them all, instalment interest plus a potential instalment penalty apply.

What to do: Set a calendar reminder for March 15, June 15, September 15, and December 15 each year you cross the $3,000 threshold.

What it costs you: Instalment interest is around 8% annualized. Skipping all four on a $12,000 instalment requirement typically adds $400–$600 to your bill.

11. Mishandling the HST “Quick Method”

GST/HST-registered small businesses with < $400,000 in annual sales can use the Quick Method, which simplifies remittance by using a flat rate instead of tracking HST paid on each expense.

Quick Method rates for 2025 (approximately):

Service-based business in HST province: 8.8% of HST-inclusive revenue
Goods-reselling business in HST province: 4.4%

Check: You must elect the Quick Method via Form GST74 before the reporting period begins — you cannot apply it retroactively mid-year. Many small service businesses save money with the Quick Method but miss the election window.

What it costs you: A service-based sole proprietor billing $60,000/year in Ontario saves roughly $800/year using the Quick Method vs the Regular Method. Missing the election means paying full HST for that year.

12. Over-Claiming Start-Up Costs as Current-Year Expenses

Start-up expenses incurred before the business is in operation (generating revenue) are generally capital in nature — not deductible in full against later-year income. Pre-operational expenses are only deductible from the date the business commenced activity.

What to do: Distinguish between pre-operational exploration costs (not deductible or only deductible as Eligible Capital Property) and operational costs incurred after opening (fully deductible under normal T2125 rules).

What it costs you: A freelance consultant who started paying for a website, business cards, and a co-working membership in October 2025 but did not bill the first client until January 2026 has no deductible business expenses on the 2025 T2125 — those costs carry into 2026 instead.

Final Pre-Submit Checklist

Use the self-employment tax calculator to estimate your 2025 balance owing before April 30. File the full T1 + T2125 any time before June 15, 2026 — but pay what you owe by April 30 to avoid arrears interest.