A held-back ten percent doesn't just sit on the balance sheet waiting for release. It carries its own tax timing, set separately from the progress payment it was carved out of.
Key takeaways
GST/HST is ordinarily payable on the earlier of two dates: “the day the consideration for the supply is paid and the day the consideration for the supply becomes due.” That's the baseline for every invoice on a construction contract — materials, labour, equipment rental.
Holdback breaks from that baseline. Section 168(7) of the Excise Tax Act carves out a specific rule for “an agreement in writing for the construction, renovation or alteration of, or repair to, any real property”: where a recipient retains part of the consideration pending full and satisfactory performance, “tax … calculated on the value of that part of the consideration, is payable on the earlier of the day that part is paid and the day it becomes payable.” In other words, the tax clock on the retained slice doesn't start ticking with the rest of the invoice — it starts on the holdback's own release date.
That trigger date is set by the construction contract and, behind it, by provincial lien legislation — and the three largest provinces don't agree on when it lands.
In Ontario, the standard holdback is ten percent, and “every payer must hold back ten per cent of the value of the work as it is done or certified” Since 1 January 2026 that release is mandatory rather than the payer's option: the owner publishes notice within a set window after each contract anniversary, and the money then flows down the chain.
In Alberta, the trigger is different in kind, not just in date: the holdback is retained for “a period of 60 days … from the date of issue of a certificate of substantial performance … or … the date of completion of the contract”, not on a contract anniversary. In British Columbia it runs from a certificate of completion too, but for a shorter window: the holdback period “expires at the end of 55 days after the certificate of completion is issued.” Same ten percent in all three provinces — three different clocks for when it comes due.
Three provinces, three different release mechanics, is the headline — but the practical risk is smaller than it sounds if the trigger date is recorded when the certificate or notice is issued, not reconstructed later from memory at filing time. The document that fixes the date — the certificate of substantial performance in Alberta and BC, the anniversary notice in Ontario — is also the only real evidence for why tax landed in the period it did if a return is ever queried.
A contractor working across more than one province on a multi-year build-out has, in effect, several holdback clocks running at once, each keyed to that job's own province and its own certificate date. Treating them as one national rule is the single most common way this gets misreported.
The practical consequence is that a contractor doesn't remit tax on the holdback portion of a job in the same reporting period as the progress payment it was carved out of. It sits until the province-specific release date arrives — which also means it doesn't generate an early ITC claim for the payer on that slice, and a contractor's own WIP schedule should carry the holdback receivable as a distinct line so the tax timing doesn't get missed at year-end.
Because that release date is set by contract and by provincial statute rather than by when the crew finished the work, getting the governing province right matters here too: the province the real property sits in governs, and a multi-province contractor tracking several jobs needs the release trigger recorded job by job, not assumed from head office's home province.
The federal record-keeping baseline applies to holdback documentation the same as everything else. Under the Income Tax Act, records must be kept “until the expiration of six years from the end of the last taxation year” and electronic records must be retained “in an electronically readable format.” The GST/HST equivalent runs on the same six-year clock.
That means the substantial performance certificate, the annual-release notice, or whatever document fixes the release date under the applicable provincial Act needs to be filed and kept — it's the evidence for why tax was reported when it was, if the return is ever reviewed.
A worked example
A $600,000.00 Ontario subcontract has $60,000.00 (10%) held back. The certificate of substantial performance is published, and under the contract's annual-release terms the holdback becomes payable 14 days after the relevant contract anniversary. GST/HST on the $540,000.00 already invoiced and paid was remitted in the periods those progress payments were made, in the ordinary course.
The $60,000.00 holdback is different: no tax on that amount is payable until the earlier of it actually being paid or that contract-anniversary release date arriving. If the subcontractor's reporting period ends before the release date, the holdback simply isn't in that period's net tax calculation at all — it lands in the period the release date falls in, whichever of the two events under s.168(7) happens first.
The holdback percentage applies to the value of the work — the GST/HST timing rule in s.168(7) is about when tax on that retained amount becomes payable, not about the payer withholding tax separately. The two are easy to conflate on an invoice; they're distinct concepts under the Act.
Provincial lien Acts generally set a fallback trigger tied to abandonment or termination of the contract, alongside the certificate-based one. Check the specific provincial Act governing the contract and confirm the applicable trigger with an accountant — it changes the answer.
The mechanism in s.168(7) applies at whichever tier of the chain is retaining part of the consideration under a written construction agreement — it isn't limited to the prime contract. Each tier holding back from the one below it applies the same timing logic to its own holdback.
They're separate questions that often get bundled together. Revenue recognition on a construction job runs on percent-of-completion, tracking costs and billings as the job progresses, independently of the holdback's GST/HST timing — a job can be fully recognised on the WIP schedule while its holdback tax is still sitting on the province's release clock.
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