Quick answer: A mismatch letter means the CRA holds a slip, a T4, T5 or similar. That does not agree with a return, and it will generally assess based on the slip unless something is corrected. The fix depends on which side is wrong: a wrong slip gets amended by whoever issued it; a wrong return gets adjusted. For owner-managers who issue their own slips, both sides are yours, which is inconvenient and also means you can actually fix it.
Why the slip usually wins by default
Slips are third-party data; returns are self-reported. When they disagree, the system’s default is to trust the slip and adjust the return. That default is rebuttable, but only by correcting whichever document is actually wrong, through its own correction channel. Arguing with the letter while both documents stand unchanged fixes nothing.
The owner-manager version
When your corporation issued the slip, the mismatch is an internal bookkeeping question wearing a CRA envelope: did the slip report what was actually paid, and did the personal return report what the slip says? The usual culprits are salary accrued but reported inconsistently, a shareholder loan reclassified late, or an amended amount that only got amended on one side.
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 book the consult from there.
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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