Quick answer: A mismatch letter means a CRA-held slip (a T4, T5 or similar) disagrees with a return, and the CRA will assess on the slip unless one is corrected. A wrong slip is amended by its issuer; a wrong return is adjusted. If you issue your own slips, both sides are yours to fix.
A T4 mismatch is more often a remittance posted to the wrong period than an amount that was never paid. Ask where to look first.
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Why the slip usually wins by default
Slips are third-party data; returns are self-reported. The system trusts the slip, but you can rebut it by correcting the wrong document through its own channel. Arguing while both documents stand fixes nothing.
The owner-manager version
When your corporation issued the slip, the question is internal: did the slip report what was paid, and did the personal return match it? Common causes: salary accrued but reported inconsistently, a shareholder loan reclassified late, or an amendment made on one side only.
A mismatch is a reconciliation that did not happen during the year, which is what payroll run so the two agree in the first place is for.
Fix it in the right order
- Find the true number first — from the ledger, not from either document.
- Correct the wrong document — amended slip through the slip system, or an adjustment to the return. Not a letter explaining; a correction filed.
- Then respond to the letter, quoting the reference number, stating what was corrected and where.
Done in that order, mismatches close quietly. Done as correspondence-first, they generate reassessments that then need objections — the expensive path to the same destination.
Fastest first step: email what you’re facing to info@everstonecpa.com — reply within one business day, and we take it from there by email.
General information, not tax advice. The document in your hand and its own dates govern.
Common questions about T4 mismatch
The slip is from someone else and it is wrong. What now?+
Can I just pay the difference and move on?+
Will this trigger a review of everything else?+
We issued the slip ourselves. How fast can this be fixed?+
Other CRA letters, decoded
Not sure which letter you have? Start with the full list and match what yours says.
One letter often follows another. These cover the ones owner-managers see most.
Two documents, one truth
Email both sides of the mismatch — we identify which to fix and file the correction.
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