T4 boxes: what each one reports and which T1 line it feeds

What does each T4 box report, and where does it go on the T1?

The CRA's employer instructions cover each numbered box, and its slip guide for individuals gives the matching line on the return canada.ca. Read the two together and the whole slip fits in one table canada.ca.

The six unnumbered boxes at the bottom are the Other information area, where the employer enters a code from 30 to 95 and an amount canada.ca. Some codes are already inside box 14 and some are not, which is the single biggest source of double counting. The full code list is on T4 other information codes, and what builds box 14 is on T4 box 14. Allocations from an employees profit sharing plan stay off the T4 and go on a T4PS slip.

Two boxes come with conditions worth knowing. Box 20 is generally deductible in full on line 20700, but the deduction can be limited when contributions top $3,500 and include past service before 1990 canada.ca. Box 22 excludes anything withheld under a garnishee or a requirement to pay, so those amounts never reach line 43700 canada.ca.

How does a $90,000 Ontario salary fill a 2026 T4, box by box?

Say your client employs one Ontario employee for all of 2026 at a $90,000 salary. The employee drives a company car with a $3,000 taxable benefit, contributes 5% of salary to a money purchase RPP that the employer matches, pays $1,000 of union dues through payroll under a no receipt agreement, gives $520 to a registered charity through payroll, and has family dental coverage.

Each cap comes from the CRA's 2026 tables: $68,900 of insurable earnings at 1.63% canada.ca, a $74,600 YMPE with a $3,500 exemption at 5.95% canada.ca, and an $85,000 YAMPE at 4% for CPP2 canada.ca. Box 16A only gets an amount once box 16 already shows the full CPP maximum canada.ca.

The CPP split is the step software hides. Box 16 is one number, but the base 4.95% earns a credit that can't create a refund while the 1% first additional contribution and all of CPP2 are deductions canada.ca. Schedule 8 splits the $4,230.45 into $3,519.45 for line 30800 and $711 for line 22215 canada.ca. The $9,000 PA isn't income or a deduction. It reduces your client's 2027 RRSP room canada.ca, and the formula is on pension adjustment calculation.

Why boxes 24 and 26 stop at a cap when box 14 never does

Box 24 holds insurable earnings up to the year's maximum, and box 26 holds pensionable earnings up to the additional maximum, which since 2024 includes the CPP2 band canada.ca. Box 14 has no ceiling. RC4120 says boxes 14 and 24, and boxes 14 and 26, are often the same amount canada.ca, which only holds for an employee under both caps with no non cash benefits.

Neither box goes on a line of the return. The CRA treats box 24 and box 26 as information it uses to check for EI and CPP overpayments on lines 45000 and 44800 canada.ca. That matters for an employee with two jobs, where each employer deducts up to the maximum separately; see CPP overpayment refund, CPP max 2026 and EI max 2026.

Quebec slips swap boxes. Box 17 and 17A carry QPP and QPP2 instead of 16 and 16A, box 18 uses the lower Quebec EI rate (1.30% for 2026, a $895.70 maximum) canada.ca, and boxes 55 and 56 report PPIP premiums and insurable earnings, with a $103,000 PPIP maximum for 2026 revenuquebec.ca. An employee resident outside Quebec adds box 55 to box 18 on line 31200 canada.ca.

When does a box show 0, and when does it stay blank?

The default is blank. The CRA says to leave boxes that don't apply empty and never to write "nil" or "N/A", negative amounts, dollar signs or dashes canada.ca. Three boxes break the rule: enter 0 in box 24 when there are no insurable earnings and box 18 is empty, 0 in box 26 when there are no pensionable earnings and boxes 16, 16A, 17 and 17A are empty, and 0 in box 56 when there are no PPIP insurable earnings canada.ca.

Box 28 is for a full reporting period exemption only. Don't check CPP/QPP when box 26 has an amount or the employee gave you a CPT30, and don't check EI when box 18 or 24 is used canada.ca. Box 29 takes a code only when one applies: 11 placement agency workers, 12 taxi drivers, 13 barbers and hairdressers, 14 a prescribed salary deferral withdrawal, 15 the Seasonal Agricultural Workers Program, 16 a detached employee under a social security agreement, 17 fishing income canada.ca.

Two identification boxes trip up new payroll files. Box 12 gets nine zeros if the employee never gave a SIN, and box 54 goes only on the employer and CRA copies, never on the employee's copy canada.ca. For filing dates, see T4 slip deadline.

Box 45 and box 52 never change the tax owing, but both are checked

Box 45 has been mandatory since the 2023 calendar year. It reports whether the employee or any family member was eligible on December 31 to access dental coverage your client offered canada.ca.

Report what was offered, not whether the employee used it, opted out or refused it, and use code 1 for someone no longer eligible on December 31 canada.ca. Health Canada uses the code in Canadian Dental Care Plan eligibility reviews, and a wrong or blank code can cost $100 per incorrect slip canada.ca. More on each code is on T4 box 45.

Box 52 is reported in dollars only, with the 7 digit plan number in box 50, and it stays blank when the PA is zero or negative, when the employee died in the year, or when no new pension credits accrued canada.ca. Your client enters it on line 20600, but the CRA says it isn't income or a deduction: it sets next year's RRSP limit canada.ca.

Which situations need more than one T4 for the same employee?

Three situations do. An employee who worked in more than one province or territory gets a separate slip for each, with box 10 changed and each slip carrying only that period's earnings canada.ca. An employee with more than six Other information codes gets an additional slip that repeats only the identification, province, exempt status and zero pensionable and insurable earnings, and reports each code once canada.ca. And box 14 can hold at most 10 digits including cents, so pay above that needs another slip.

Income is reported for the year it was paid, not the year it was earned, so a 2025 raise paid in 2026 goes on the 2026 slip canada.ca. Union dues in box 44 already include any GST/HST, and your client must not claim the same dues again from a union receipt canada.ca. A mistake on a filed slip is fixed with an amended slip, never a negative amount on next year's; see T4 amendment.