What triggers a PIER review versus a full payroll audit by CRA?

A PIER review is triggered by a specific kind of discrepancy: CRA's system flags a mismatch between the earnings your business reported for employees and the CPP and EI amounts that should have been withheld and remitted based on those earnings. It's a narrow, calculation-focused check aimed specifically at CPP/EI accuracy, and it's generally a lighter-touch, more routine process than a full audit.

A full payroll audit is broader in scope. Rather than focusing narrowly on whether your CPP/EI numbers reconcile against reported earnings, a full audit examines your overall payroll compliance picture — income tax withholding, taxable benefits, worker classification between employees and contractors, and other aspects of how your payroll is run, not just the PIER program's specific earnings-matching focus.

The difference is really one of scope and depth, not of legal seriousness on its own — a PIER finding can still lead to real financial consequences if it uncovers under-remittance, just as a full audit can. But a PIER letter specifically signals a targeted CPP/EI discrepancy CRA wants explained or corrected, while a full audit signals CRA is examining your payroll practices more comprehensively. Understanding which one you're facing helps you and your advisor scope the right response and gather the right records from the start.