The job being done and the file being safe to close aren't the same date. Tax law alone puts a six-year floor under almost everything.
Short answer
Tax records outlive almost everything else by law -- six years minimum under the Income Tax Act -- and several provinces' lien and trust remedies stay live for a year or more after the last invoice, so “the job is closed” and “you can throw out the file” are not the same date.
The Income Tax Act requires every person carrying on business to keep records and books of account, and to retain them “until the expiration of six years from the end of the last taxation year to which the records and books of account relate.” Electronic records have to stay “in an electronically readable format” for that same period -- and the trap worth knowing is that if no return was ever filed for a given year, the six-year clock never starts on that year's records at all. A corporation's minute books and share-ownership records get a different rule again: two years after the corporation is dissolved, under the Income Tax Regulations. If your business pays subcontractors for construction activities, the T5018 information return runs on its own clock, filed “within six months after the end of the reporting period” once you've chosen a calendar or fiscal reporting basis.
Ontario's Construction Act gives a lien claimant 60 days to preserve and 90 more to perfect, but that's the start of the exposure window, not the end of the file -- a wilfully exaggerated lien or a trust claim can still expose a director well after those two windows close, per treadstonelaw's own construction-lien coverage. British Columbia is more explicit: a trust action “must not be commenced later than one year” after the head contract or the improvement is completed, abandoned or terminated, and an enforcement action plus a certificate of pending litigation has to register “not later than one year from the date of its filing.” Manitoba runs longer again -- a registered lien runs two years before an action must be commenced, unless the owner serves a notice that shortens it to 30 days.
In practice that means tax records for six years minimum, warranty and closeout documentation for as long as the applicable warranty runs -- up to seven years from the Agreement of Purchase and Sale under Tarion -- and lien or trust-relevant correspondence for at least a year past substantial completion, longer in Manitoba. The file thrown out at the six-month mark because “the job's done” is the one that costs someone a defence three years later. See how do we hand over a building cleanly and who keeps the as-builts for what belongs in that file in the first place.
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