Glossary of factor symbols
Who this is for: Developers reading API breakdown fields or CONFORMANCE vectors who need plain English for each symbol.
When you finish: You can map any factor symbol in a response to its T4127 (Payroll Deductions Formulas) step and open the CRA payroll formulas hub.
Amounts in API responses are decimal strings in cents; this page defines names only.
A
Annual taxable income.
Source: T4127 Chapter 4, Step 1
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
R
Federal tax rate that applies to the annual taxable income A.
Source: T4127 Chapter 8, Table 8.1
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
K
Federal constant; the tax overcharged when applying the higher federal rates to A.
Source: T4127 Chapter 8, Table 8.1
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
K1
Federal non-refundable personal tax credit (lowest federal tax rate × TC).
Source: T4127 Chapter 4, Step 2
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
K2
Federal tax credit for base CPP contributions and EI premiums for the year.
Source: T4127 Chapter 4, Step 2
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
K4
Federal non-refundable tax credit calculated using the Canada employment amount.
Source: T4127 Chapter 4, Step 2
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
T3
Annual basic federal tax.
Source: T4127 Chapter 4, Step 2
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
T1
Annual federal tax deduction.
Source: T4127 Chapter 4, Step 3
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
V
Provincial or territorial tax rate for the year.
Source: T4127 Chapter 8, Table 8.1
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
KP
Provincial or territorial constant.
Source: T4127 Chapter 8, Table 8.1
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
K1P
Provincial or territorial non-refundable personal tax credit (lowest provincial rate × TCP).
Source: T4127 Chapter 4, Step 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
K2P
Provincial or territorial tax credit for base CPP contributions and EI premiums for the year.
Source: T4127 Chapter 4, Step 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
T4
Annual basic provincial or territorial tax.
Source: T4127 Chapter 4, Step 4
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
V1
Provincial surtax calculated on the basic provincial tax (Ontario only).
Source: T4127 Chapter 4, Step 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
V2
Ontario Health Premium calculated on taxable income.
Source: T4127 Chapter 4, Step 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
S
Provincial tax reduction (Ontario and British Columbia).
Source: T4127 Chapter 4, Step 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
T2
Annual provincial or territorial tax deduction (except Quebec).
Source: T4127 Chapter 4, Step 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
T
Estimated federal and provincial or territorial tax deductions for the pay period: round((T1+T2)/P)+L. This is the combined Step 6 quotient. It may differ by one cent from employee.total_tax, which is the sum of the separately rounded federal and provincial lines PDOC displays (round(T1/P)+L and round(T2/P)). Compare screen totals to employee.total_tax; keep breakdown.T as the T4127 figure.
Source: T4127 Chapter 4, Step 6
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
TB
Tax on the current bonus or retroactive pay: the difference between annual tax (T1+T2) with the non-periodic payment and without it, floored at zero. If A with the bonus is at or below $5,000, a flat 15% of the bonus is used instead.
Source: T4127 Chapter 4, bonuses and retroactive pay
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
M
Year-to-date federal and provincial tax already deducted on periodic pay (Option 2). Does not include extra tax requested (L) or tax on bonuses (M1).
Source: T4127 Chapter 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
M1
Accumulated federal and provincial tax deductions on non-periodic payments such as bonuses, to the last pay period (Option 2).
Source: T4127 Chapter 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
C
Canada (or Quebec) Pension Plan contributions for the pay period.
Source: T4127 Chapter 6
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
C2
Second additional Canada (or Quebec) Pension Plan contributions for the pay period.
Source: T4127 Chapter 6
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
EI
Employment insurance premiums for the pay period.
Source: T4127 Chapter 7
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
F5
Deductions for Canada Pension Plan additional contributions for the pay period.
Source: T4127 Chapter 4, Step 1
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
BPAF
Federal Basic Personal Amount.
Source: T4127 Chapter 2; Table 8.2
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
K3
Other federal non-refundable tax credits authorized by a tax services office or tax centre.
Source: T4127 Chapter 4, Step 2
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
K3P
Other provincial or territorial non-refundable tax credits authorized by a tax services office or tax centre.
Source: T4127 Chapter 4, Step 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
K4P
Territorial non-refundable tax credit calculated using the provincial or territorial Canada employment amount.
Source: T4127 Chapter 4, Step 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
K5P
Provincial supplemental non-refundable tax credit (lowest provincial tax rate).
Source: T4127 Chapter 4, Step 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
LCF
Federal labour-sponsored funds tax credit.
Source: T4127 Chapter 4, Step 3
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
LCP
Provincial or territorial labour-sponsored funds tax credit.
Source: T4127 Chapter 4, Step 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
Y
Additional Ontario tax-reduction amount based on the number of eligible dependants, used in Factor S.
Source: T4127 Chapter 4, Step 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
F5A
CPP additional-contribution deduction for the pay period taken from periodic income.
Source: T4127 Chapter 4, Step 1
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
F5B
CPP additional-contribution deduction for the pay period taken from the non-periodic payment.
Source: T4127 Chapter 4, Step 1
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
D
Employee’s year-to-date (before the pay period) Canada Pension Plan contribution with the employer.
Source: T4127 Chapter 6
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
D1
Employee’s year-to-date (before the pay period) employment insurance premium with the employer.
Source: T4127 Chapter 7
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
D2
Employee’s year-to-date (before the pay period) second additional CPP contribution with the employer.
Source: T4127 Chapter 6
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
P
The number of pay periods in the year.
Source: T4127 Chapter 4, Step 1
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
PR
The number of pay periods left in the year (including the current pay period).
Source: T4127 Chapter 4, Step 1
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
PM
Total months during which CPP and/or QPP contributions are required (used to prorate the maximum contribution).
Source: T4127 Chapter 6
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
S1
Option 2 cumulative-averaging pair: total pay periods / current pay-period number (for example 52/1, 52/2). Never a binary float. Option 1 serializes as P/1.
Source: T4127 Chapter 5
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
CEA
Canada Employment Amount, a non-refundable tax credit used in the calculation for K4 and K4P.
Source: T4127 Chapter 8, Table 8.2
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
TC
Total claim amount reported on federal Form TD1.
Source: T4127 Chapter 2
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
TCP
Total claim amount reported on the provincial or territorial Form TD1.
Source: T4127 Chapter 2
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
IE
Insurable earnings for the pay period, including insurable taxable benefits, bonuses, and retroactive pay increases.
Source: T4127 Chapter 7
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
QPIP
Quebec Parental Insurance Plan premium for the pay period.
Source: T4127 Chapter 8, Table 8.29
CRA: https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/payroll/payroll-deductions-formulas.html
Last reviewed: 2026-09-20 Engine: 0.1.0