What happens if CRA finds my Ontario business under-remitted payroll deductions in a PIER review?

If a PIER review finds that your business under-remitted CPP or EI deductions, your business becomes responsible for making up that shortfall, and in some circumstances that can include both the employer and employee portions of the amounts that should have been withheld and remitted. On top of the shortfall itself, CRA can also apply penalties and interest, which adds to the overall cost of resolving the discrepancy.

This is worth taking seriously beyond just the dollar amount at stake, because unremitted source deductions connect to a broader risk: if the shortfall ultimately isn't paid, the corporation's directors can potentially become personally liable for the unremitted amounts. This is the same director's-liability concept that applies more broadly to unremitted payroll deductions and GST/HST, and it means a PIER finding isn't purely a corporate-level problem that stops at the business — it can reach the people running it if it goes unresolved.

Given that, the most sensible response to a PIER finding is to address the shortfall promptly, confirm exactly what's owed, and correct the underlying payroll calculation going forward so the same discrepancy doesn't recur in future reporting periods, rather than treating the letter as something to deal with only when convenient.