Redact a T4 SlipBox 12 Is Your SIN
Your Social Insurance Number sits in box 12 of every T4. Most people emailing a T4 are proving income, and income is boxes 14 and 22, not box 12. Cover it in your browser. Nothing uploaded.
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Where the SIN is, and who actually needs it
The CRA’s own employers’ guide is explicit: box 12 of the T4 slip is the employee’s social insurance number. Every T4 you have ever received carries it near the top of the slip.
Your employer needs it, and the CRA needs it. That is why it is printed there. The question is who else ends up holding a copy once you start emailing the slip around as proof of income.
The Office of the Privacy Commissioner of Canada is clear that a landlord does NOT require your SIN, and that it is not needed for a basic credit check. The OPC “generally recommends that individuals do not give the SIN to a private-sector organization unless there is a legal requirement to do so”.
The OPC also notes the SIN should not be used as a general identifier. So a T4 sent to a landlord, a broker or a rental platform can have box 12 covered without affecting anything the recipient is legitimately assessing.
What To Cover On A T4
Income stays. The identifier goes.
Cover these
- Box 12, your social insurance number
- Your full home address
- Employee or payroll number, if shown
- Employer account number, if not needed
Leave these visible
- Your name
- Employer name
- Tax year
- Box 14, employment income
- Box 22, income tax deducted
- Boxes 16 to 18, CPP and EI, if relevant
How It Works
Under a minute, and the file never leaves your device.
Open the T4
Drop the PDF or screenshot in. Your browser handles it locally.
Cover box 12
Black out all nine digits of the SIN, plus your address.
Email the redacted copy
Export and attach that version instead of the original.
Your documents never leave your browser
A SIN is permanent. You cannot rotate it after a leak the way you would change a password, so every copy sitting in an inbox or on a rental platform is a lasting exposure. That is the whole reason the Privacy Commissioner advises against handing it to private-sector organisations without a legal requirement.
RedactID does not add another copy. There is no upload step, because the redaction runs in the page you are already looking at. We never receive your file, so we cannot lose it.
How that actually worksCommon Questions
Which box on a T4 is the SIN?
Box 12. The CRA's Employers' Guide to filing the T4 slip states that box 12 is the employee's social insurance number, and instructs employers to enter nine zeros if they do not have it. It is in the same position on every T4.
Do I have to give my SIN to a landlord?
No. The Office of the Privacy Commissioner of Canada says a landlord does not require your SIN, and that it is not needed for a basic credit check. It generally recommends not giving your SIN to a private-sector organisation unless there is a legal requirement. A landlord may ask, but cannot require it, and you can offer other identification instead.
What should I leave visible on a T4?
Your name, the employer name, the tax year, box 14 employment income and box 22 income tax deducted. Those are what a lender, accountant or landlord is actually reading. The SIN in box 12 contributes nothing to an income assessment.
Can I redact a T4 I am sending to my accountant?
Your accountant almost certainly does need your SIN to file on your behalf, so this is a case where the number is legitimately required. Send that one intact through a secure channel. Redaction is for the copies going to people who are only checking your income.
What other Canadian documents show my SIN?
A T4A, a CRA Notice of Assessment, RRSP contribution receipts and often a pay stub. Anywhere you send proof of income, check for the SIN first, because these documents were designed for the CRA rather than for landlords.
Does RedactID upload my T4?
No. Redaction runs in your browser on your own device. The file is not uploaded, not stored, and never reaches our servers.