HST on Building a Custom Home on Your Own Lot in Ontario

You already own the land. You've hired a contractor — or you're planning to manage the build yourself. Either way, you're about to discover that building a custom home on your own lot in Ontario is not an HST-free exercise.

Many people assume that because they already paid land transfer tax on the lot, and because they're building for their own use rather than to sell, the HST exposure is minimal. That assumption is often right about the self-supply rule for a genuine personal-use build, because an individual who builds otherwise than in the course of a business is not a “builder”, and s. 191 (5) exempts individual builders who live in the home. Where you are a builder, for example because you build in the course of a business, the federal Excise Tax Act's self-supply rule deems you to have sold — and repurchased — the home when it is first occupied, triggering HST on the fair market value of the completed property. Either way, you pay HST on the construction itself. Understanding when the self-supply rule applies, what rebate offsets your HST cost, and what records you need is essential before you break ground. All figures and thresholds mentioned below were accurate as of writing — verify current amounts with CRA or a qualified accountant before filing.

Why Building on Your Own Lot Isn't HST-Free

When a developer builds and sells a new home, the HST is embedded in the purchase price and the developer remits it. When you build on your own lot, there is no sale, so the Act's self-supply rule exists to ensure new housing is taxed consistently regardless of who builds it. The rule treats a builder as both the seller and the buyer — but there is an important carve-out: an individual who builds primarily as their own (or a relation's) residence and claims no input tax credits is exempt from self-supply (s. 191 (5)). Where the rule does apply, the builder owes HST on the fair market value of the home (and the land underneath it) as a completed unit, even though no cheque changes hands. Even where it does not, you pay HST on the construction invoices, as described below.

When the Self-Supply Rule Applies

1. You do not become a “builder” under the Excise Tax Act unless you build in the course of a business or an adventure or concern in the nature of trade. The Act defines builder broadly. If you hire a general contractor to build a home on your land as your own place of residence, otherwise than in the course of a business, you are not a builder for GST/HST purposes and the self-supply rule does not apply.
2. The trigger event occurs. If you are a builder, the self-supply is triggered when you, or someone you give possession to under a lease, licence or similar arrangement, first occupies the home as a place of residence, and the deemed supply date is the later of that time and substantial completion.
3. CRA deems a taxable sale at fair market value. For a builder, on the trigger date, you are treated as having sold the completed home and land to yourself at fair market value. HST applies to that full fair market value.
4. The HST owing is calculated. For a builder, apply the HST rate (13% in Ontario as of writing — confirm with CRA) to the fair market value of the property on the trigger date. This is the gross tax.
5. Available rebates are subtracted. A rebate described below may reduce the net amount owing.
6. The builder files and remits. A builder must file a GST/HST return and remit the net tax by the deadline. Failure to file on time can result in interest and penalties.

Hiring a GC vs. Acting as Your Own General Contractor

How you structure the build affects your HST exposure at the construction stage — though the self-supply rule applies in either model only if you are a builder under the Excise Tax Act, for example because you build in the course of a business or an adventure or concern in the nature of trade.

Model A: Hiring a General Contractor

• The GC is a registrant; they charge you HST on their invoices (labour and materials they supply).
• You pay HST on every progress draw.
• If you are building your own residence otherwise than in a business, you cannot claim input tax credits (ITCs) on those payments, because ITCs are only for inputs used in commercial activities; the HST you pay instead supports the owner-built home rebate.
• For a home built as your own residence, your HST cost is the HST you pay on the GC's invoices, less any owner-built home rebate.
• Record-keeping is simpler because one entity (the GC) is accountable for most invoices.

Model B: You Are the General Contractor

• You hire subtrades directly (framing, electrical, plumbing, HVAC, etc.).
• Each registered subtrade charges you HST; for a home built as your own residence you cannot claim ITCs, so keep each invoice for the rebate claim.
• You also pay HST on materials you purchase directly.
• You have maximum control over cost but significantly more invoices to track and more exposure if a subtrade fails to properly charge HST or you lose an invoice you need for the rebate claim.
• Your HST position is the same in principle, but there are more invoices to assemble for the rebate claim.

HST on Labour and Materials: What's Taxable

HST applies to substantially all costs in a residential construction project:

• Labour — all invoices from registered subtrades and the GC carry HST.
• Materials — lumber, drywall, windows, doors, fixtures, appliances (most), flooring, and finishes are all taxable supplies.
• Professional fees — architect, engineer, and designer fees are taxable.
• Notable zero-rated or exempt items are rare in residential construction; do not assume any line item is HST-free without confirming with your accountant.

For a home built as your own residence you cannot claim ITCs, but the HST you pay on construction inputs supports the owner-built home rebate. Keep every invoice.

The Owner-Built Homes Rebate vs. The New Housing Rebate

The rebate for owner-built homes has a federal part and an Ontario part, claimed together, each with its own fair market value rules (confirm current thresholds with CRA):

New Housing Rebate (NHR): The federal part is available to owner-builders below a certain fair market value threshold, while the Ontario part may be available even above it. The federal part phases out as fair market value increases above that threshold, and disappears entirely above the upper limit. The NHR is claimed on CRA Form GST191.

Owner-Built Homes Rebate (OBHR): This is the specific rebate stream for individuals who build on their own lot (as opposed to purchasing a newly built home from a developer). It uses Form GST191 with the Ontario schedule. The calculation uses one fair market value for the house that includes the land and any other buildings, an important point discussed below.

If you intend to use the home as your primary place of residence, you are generally eligible to apply. If you build for rental or resale, different rules apply and the rebate may not be available.

How Land Value Affects the Rebate

The rebate is calculated against the full fair market value of the property — land included. If you paid $300,000 for the lot several years ago and it has since appreciated, its value when construction is substantially completed is what matters, not your historical cost. A high land value can push total fair market value above rebate thresholds even if the build itself was modest, reducing or eliminating the rebate. Get a proper appraisal of the value when construction is substantially completed and keep it on file.

Records You Must Keep

CRA can audit your filings years after the fact. Maintain organized records of:

• All contractor and subtrade invoices showing HST registration numbers and amounts
• Materials receipts for any supplies you purchased directly
• Your building permit and occupancy permit
• A timeline of construction milestones and the date of first occupancy
• The appraisal or other evidence of fair market value when construction was substantially completed
• All HST invoices and any GST/HST returns filed
• Proof of your intent to use the home as a primary residence

The Filing Deadline

The owner-built rebate application must generally be filed within two years after construction is substantially completed; the deadline is worked out differently if you move in during construction or sell the home before anyone lives in it. Missing this window forfeits the rebate — CRA will not extend it in most circumstances. Set a calendar reminder well before the two-year mark and engage your accountant or lawyer early.

Frequently asked questions