Form GST191 is the application for the GST/HST new housing rebate on an owner-built home. If you built a house, had one built for you, or substantially renovated one, this is the form that gets you your money back.
It used to be reasonably straightforward. It isn’t any more.
The rebate programs that landed in 2025 and 2026 added routes, thresholds and interactions that didn’t exist before, and the form grew to accommodate them. What follows isn’t a line-by-line walkthrough — the CRA’s own guide, RC4028, does that. This is the shorter and more useful list: the places where these claims actually go wrong.
Before you write anything: know which claim you’re making
This is the first obstacle, and a surprising number of people never clear it.
There are now several distinct routes, and they aren’t alternatives you pick between on preference. Which one applies is a question of fact, and it determines which sections of the form you complete.
The classic owner-built rebate. The long-standing program. Section 1 of the form.
The first-time home buyers’ rebate. Newer, larger, and with its own tests. Section 2.
Ontario’s ONHAP. The Ontario New Home Affordability Payment, which provides relief equivalent to the federal portion. Administered separately by Ontario.
Working out which of these you’re in — and whether you’re in more than one — before you start filling anything in will save you considerable time. Starting the form and discovering halfway through that you’re on the wrong route means starting again.
The worksheet comes first
It’s where you list every invoice: supplier, date, amount, and the GST/HST paid. It’s tedious, and it’s also the foundation of the entire claim. The number that ends up on your rebate application comes from this worksheet.
Two practical points.
Do the worksheet properly before touching the main form. The main form asks for totals the worksheet produces, and reverse-engineering it is worse than doing it in order.
If you’re missing invoices, gather what you can before you start. Suppliers and trades will often reissue. Bank and credit card records help establish what was spent, even where the invoice itself is gone. A claim with gaps is weaker, not dead — but it’s much easier to fill the gaps before you’ve built the worksheet than after.
Substantial completion is not your final inspection
This is the single most common error we see on owner-built claims, and it matters because so much of the form depends on it.
Final inspection means the permit-issuing authority is satisfied. That’s a building-code question. It tells you the work meets the standards the municipality enforces, and it has nothing to do with the Excise Tax Act.
Substantial completion is a different test. The house is substantially complete when it’s “genuinely habitable” — plumbing working, a functioning kitchen and bathroom, somewhere you could actually move into and live.
Those two dates are often weeks or months apart, and occasionally they’re in different years. Using the inspection date because it’s the one with a certificate attached is understandable, and it’s wrong.
Get this date right first. Several other answers depend on it.
The base date is genuinely difficult
The CRA’s own guidance handles the filing deadline by referring you back to RC4028, which tells you something about how straightforward it is.
Here’s the shape of it.
Your base date is the earliest of three things:
– Two years after you or a relation first occupied the house after construction began
– The date ownership transferred to a purchaser in an exempt sale, if that happened before anyone occupied it
– The date construction was substantially completed
Your filing deadline is two years after that base date.
In the most common situation — the house is finished, then you move in — the base date is substantial completion, and you have two years from then. The CRA’s own example runs completion in April, occupancy in May, and a filing deadline two years after the April date.
But if you moved in before it was substantially complete, which happens constantly on self-builds, the calculation changes. The deadline becomes the earlier of two years after completion and four years after you first moved in.
And there’s a trap inside the trap: GST/HST that became payable more than two years after you first occupied the house generally can’t be included in the rebate calculation at all. So a long, slow finish doesn’t just complicate the deadline — it can quietly remove invoices from your claim.
If your build ran long, or you moved in before it was done, this is the part to get advice on rather than work out yourself.
Section 1: the classic rebate
This section is the most straightforward part of the form. It follows the long-standing owner-built rebate, the conditions are stable, and if your situation is simple the arithmetic is arithmetic.
Take the time on the worksheet, and this section largely fills itself.
Line R: fair market value, and why it worries people more than it should
Line R asks for the fair market value of the finished house.
People freeze at this, because “fair market value” sounds like it requires an appraiser, a report and a fee.
It doesn’t. The form asks for a reasonable figure, not a formal valuation.
The way to think about it: what would the house have fetched if you’d sold it on the day it was substantially completed? Not what you spent building it — those are different numbers, sometimes very different. Not what it’s worth today. What it was worth, on the open market, on that date.
Comparable sales in your area from around that time will get you to a defensible number. Defensible is key!
One caveat. The CRA can disagree with your figure, and on larger or unusual properties they sometimes do. If your house is substantially above local norms, or unusual enough that comparables are thin, supporting evidence is worth having. Not because the form requires it — because a review might.
Section 2: the first-time buyer part, and why it’s a time bomb
If Section 1 is the easy part, this is the opposite.
The first-time home buyers’ rebate brings in fair market value thresholds and a series of “lesser of” calculations — rebate capped at the lesser of one figure and another, with values phasing out across ranges.
Two things make this dangerous.
Small changes in value produce large changes in outcome. Once you’re into a phase-out range, a modest difference in the fair market value you entered on Line R can move the rebate by tens of thousands. The number you picked casually a page earlier suddenly matters enormously.
And the eligibility test itself is easy to fail without noticing. The first-time buyer conditions count a home owned by you or your spouse, and run on calendar years rather than rolling months. People complete this section confident they qualify, on a test they haven’t actually applied.
If your claim touches Section 2, and particularly if your fair market value is anywhere near a threshold, this is the point to stop and get it checked. It’s the part of the form where a small error is most expensive.
Don’t forget the Ontario schedule
The Ontario portion of the rebate a separate schedule — RC7191-ON — that goes with the federal form.
It’s straightforward once the federal side is right, but it does need to be filed. Claims that recover the federal portion and quietly leave the provincial portion behind are not rare, and the provincial amount is usually the larger of the two.
The honest summary
If this feels like a lot, it’s because it is. The 2025 and 2026 changes made these rebates substantially larger and substantially more complicated at the same time.
A simple owner-built claim, with clean invoices and clear dates, is a form you can complete yourself with the guide beside you.
A claim that touches the first-time buyer rules, or where occupancy came before completion, or where fair market value sits near a threshold — that’s a different exercise, and the cost of getting it wrong is measured in tens of thousands rather than hours.
If you’re not sure which of those you have, that’s exactly what a free assessment is for.