Costly mistakes when buying or selling a home in Canada (and how to avoid them)

The most expensive mistakes in a Canadian home sale rarely involve the headline price. They come from contract terms nobody read, tax relief nobody claimed, or rules that apply only in one province. Sellers lose money through long listing agreements with broad holdover clauses, quotes without HST, unexpected mortgage prepayment charges and selling too soon after buying. Buyers lose money by forgetting Toronto's second land transfer tax or Quebec's welcome tax bill, by putting a parent on title and losing part of a first-time buyer refund, and by signing new-home agreements that assume rebates they do not qualify for.

This page is the overview for Mistakes, Disputes and Official Sources. Each mistake links to the detailed guide. Amounts are illustrative.

Seller mistakes

Mistake	What it costs	How to avoid it
Comparing commission quotes without tax	13% to 15% more than you budgeted in HST provinces	Ask for every figure with GST/HST; use the commission calculator
Signing a six-month agreement with a long holdover	Paying commission on a sale after you left the agent, or paying two brokerages	Read listing agreement traps
Setting a closing date before checking the mortgage payout	A prepayment charge of thousands of dollars you could have avoided by porting or timing	Get a payout statement from your lender first
Selling within 12 months of buying	Profit taxed as business income under the federal flipping rule; in BC, the home flipping tax	Read tax on selling a home
Not reporting the sale of your principal residence	Penalties, and possible loss of the exemption	Report the designation on your return for the year of sale
Non-resident seller without a section 116 certificate	Buyer withholds 25% of the price	Apply to the CRA early
Inaccurate disclosure about the property	Claims after closing for misrepresentation or latent defects	Answer questions honestly; get legal advice

Buyer mistakes

Mistake	What it costs	How to avoid it
Forgetting Toronto's MLTT	$16,475 extra on a $1,000,000 home	See Ontario and Toronto land transfer tax
Not setting cash aside for Quebec's welcome tax	A bill of several thousand dollars weeks after closing	See Quebec welcome tax
Adding a parent to title	Part of the first-time buyer refund lost, because the parent is not a first-time buyer	Discuss the ownership structure with your lawyer before the offer
Assuming the BC first-time exemption at $880,000	No exemption above $860,000	Check thresholds in BC property transfer tax
Signing a new-home price that assumes rebates	Builder charges the rebate back on closing if you do not qualify	Read the HST schedule; see GST/HST on new homes
Ignoring the buyer agreement's fee clause	Paying your agent the shortfall when a listing offers less	See CREA and Competition Bureau
Forgetting sales tax on mortgage insurance	Cash due on closing in Ontario, Quebec and Saskatchewan	Budget for it in the closing costs checklist
Buying as a non-Canadian in a restricted area	Fine of up to $10,000 and a possible court-ordered sale	Read foreign buyer ban and non-resident taxes

Three mistakes in detail

1. The parent on title. A first-time buyer in Toronto buys a $700,000 condo and adds her mother, who owns a house, as a 50% owner to help qualify. The Ontario refund and Toronto rebate are generally reduced to the first-time buyer's share. Instead of up to $8,475 off, she gets about half, roughly $4,240. In many cases a lender will accept a guarantor or co-signer arrangement that does not require the parent on title; ask your lender and lawyer.

2. The quote without HST. A Halifax seller compares a 4% "all-in" proposal with a 3.75% proposal and picks the latter, assuming it is cheaper. The 4% figure already included HST (equivalent to about 3.51% plus 14% HST); the 3.75% did not (4.275% with tax). On a $600,000 sale, the "cheaper" one costs $25,650 instead of $24,000.

3. The sale too soon. A couple buys a house in January and sells it in November of the same year to move for work. A job relocation is one of the life events that can exempt a sale from the federal flipping rule, but they must be able to show it. Without the exemption, the gain would be fully taxed as business income and the principal residence exemption denied.

Before you sign anything

Ask for every cost in writing with tax included.
Calculate land transfer tax for your exact city.
Confirm first-time buyer status for every person going on title.
Get the mortgage payout statement before setting dates.
Read the holdover and buyer-fee clauses.
Confirm residency and citizenship rules if anyone involved is not a Canadian citizen or permanent resident.
Know where to complain if something goes wrong: see complaints and regulators, and check facts in the official sources list. The Underused Housing Tax guide covers older filing obligations for some owners.

Frequently asked questions

What is the single most expensive selling mistake?

Usually pricing, followed by commission and mortgage payout terms that were not negotiated or checked. Each can be worth more than all other costs together.

Can I fix a missed first-time buyer refund?

Often yes. Ontario and Toronto accept applications within 18 months of registration; BC has a refund process for exemptions not claimed.

Who checks that my closing costs are right?

Your lawyer or notary prepares the statement of adjustments. Ask questions about every line before closing.

Can a realtor give me tax advice?

Realtors can explain general rules but are not tax advisers. For flipping rules, non-residency or a property that was not always your principal residence, see an accountant.

Sources

Canada Revenue Agency — flipping rules, principal residence, section 116
Ontario Ministry of Finance — land transfer tax refunds
City of Toronto — MLTT
Government of British Columbia — PTT and home flipping tax
Financial Consumer Agency of Canada — mortgages and prepayment charges