Inspect the Arithmetic — CCPC Income Tax Calculator

Version 1.1
Last verified: May 2026

Transparent arithmetic is the operating system of this calculator.

This document publishes the formulae, computational structure, and assumptions used to generate the outputs displayed on the CCPC calculator page.

No opinions. No hidden assumptions. Just arithmetic.

Purpose

This calculator estimates the combined tax burden for a Canadian Controlled Private Corporation (CCPC) and its shareholder(s) for the 2025 tax year. It models:

Corporate taxable income and corporate tax (federal and provincial) on active business income.
After-tax cash inside the corporation and retained earnings after distributions.
Personal income tax, CPP, and EI for one or two shareholders receiving salary and/or dividends.
The combined corporate + personal tax burden and an effective overall tax rate on gross corporate revenue.

Definitions

Let:

Y = tax year (fixed at 2025 in this version)
P_corp = province/territory of incorporation (for corporate tax)
P_pers = province/territory of residence for shareholders (for personal tax; assumed equal to P_corp unless overridden later)
R = gross corporate revenue
X = deductible business expenses (exclude shareholder salary; salary is entered separately)
P_pre = max(0, R − X), corporate income before owner compensation (salary and employer CPP)
CPP_emp = employer CPP on T4 salary (matched to employee CPP in the payroll model, per employment)
I_corp = corporate taxable income after salary and employer CPP
SBDLimit = federal small business deduction limit (typically $500,000), applied for the chosen province using the corporate tax data files.
r_fed,SBD, r_fed,gen = federal SBD and general corporate tax rates
r_prov,SBD, r_prov,gen = provincial SBD and general corporate tax rates
Tax_fed,corp = federal corporate tax
Tax_prov,corp = provincial corporate tax
Tax_corp = total corporate tax
Cash_after = after‑tax corporate cash (before distributions)
For one shareholder:

S = salary/bonus paid to the shareholder
D_elig = eligible dividends paid
D_ne = non‑eligible dividends paid
O_pers = other personal income
D_pers = personal deductions (user‑entered estimate)

For two shareholders (income splitting):

S₁, S₂ = salary/bonus paid to shareholder 1 and 2
D_elig,1, D_elig,2 = eligible dividends to each shareholder
D_ne,1, D_ne,2 = non‑eligible dividends to each shareholder
O_pers,1, O_pers,2 = other personal income
D_pers,1, D_pers,2 = personal deductions

CPP, EI = employee CPP contributions and EI premiums on salary (per shareholder)
Tax_pers = total personal income tax (federal + provincial) for a given shareholder
Tax_pers,1, Tax_pers,2 = total personal tax for shareholders 1 and 2
Burden_total = combined corporate tax + personal income tax for all shareholders
Rate_eff = effective combined tax rate on gross revenue
RetEarn = retained earnings after all modeled distributions

Corporate Tax Arithmetic

Corporate tax is computed by the pure engine function calculateCorporateTax(taxableIncome, province) in corporate.engine.js, using corporate tax data from federal-corporate.json and provinces-corporate.json.

1. Corporate Taxable Income

P_pre = max(0, R − X)
I_corp = max(0, P_pre − S − CPP_emp) (one shareholder; S = salary to that shareholder)
I_corp = max(0, P_pre − (S₁ + S₂) − (CPP_emp,1 + CPP_emp,2)) (two shareholders)

Negative results are clipped to 0. Salary and employer CPP are deductible corporate expenses and are modeled from the salary inputs (not from X). Employee CPP and EI remain on the personal side only. Loss carryforwards, loss carrybacks, and passive investment income rules are out of scope.

2. Federal and Provincial Corporate Tax

The engine applies a simple two‑tier structure based on the small business deduction limit SBDLimit:

If I_corp ≤ SBDLimit:
  All income taxed at SBD rates.

Else:
  Income up to SBDLimit taxed at SBD rates.
  Income above SBDLimit taxed at general rates.

Federal side:

FedSBDIncome = min(I_corp, SBDLimit)
FedGenIncome = max(0, I_corp − SBDLimit)
Tax_fed,corp = FedSBDIncome × r_fed,SBD + FedGenIncome × r_fed,gen

Provincial side (using province‑specific rates and SBD limit where applicable):

ProvSBDIncome = min(I_corp, SBDLimit)
ProvGenIncome = max(0, I_corp − SBDLimit)
Tax_prov,corp = ProvSBDIncome × r_prov,SBD + ProvGenIncome × r_prov,gen

Total corporate tax and after‑tax cash:

Tax_corp = Tax_fed,corp + Tax_prov,corp
Cash_after = I_corp − Tax_corp

Distributions and Retained Earnings

3. Single‑Shareholder Scenario

Salary is already reflected in I_corp (and in Cash_after). Retained earnings compare after‑tax corporate cash only to dividends paid from post‑corporate‑tax funds:

Dist_single = D_elig + D_ne
RetEarn = max(0, Cash_after − Dist_single)

If modeled dividends exceed after‑tax corporate cash, retained earnings are clipped to zero rather than displaying negative corporate equity. The corporate side does not enforce balance‑sheet constraints beyond this max‑zero clipping; over‑distributions relative to Cash_after are not flagged separately in this version.

4. Two‑Shareholder (Income Splitting) Scenario

When “income splitting” is enabled, the same rule applies using total dividends to both shareholders:

Dist_split = (D_elig,1 + D_ne,1) + (D_elig,2 + D_ne,2)
RetEarn = max(0, Cash_after − Dist_split)

Personal Tax Arithmetic

Personal tax for each shareholder is computed by the shared personal tax engine computePersonalTax() in /calculators/canada-income-tax/js/tax.engine.js, using the same brackets, credits, CPP/EI logic, and dividend rules as the standalone Canada Personal Income Tax Calculator.

5. Mapping Corporate Inputs to Personal Inputs

For each shareholder, the CCPC bridge module computeCCPCTax() constructs a personal tax input object:

Employment income = salary from the corporation (S, S₁, or S₂).
Eligible and non‑eligible dividends = dividends from the corporation.
Other income = O_pers, O_pers,1, or O_pers,2.
RRSP and FHSA deductions = 0 in this CCPC calculator.
Estimated deductions = D_pers, D_pers,1, or D_pers,2.
Tax already paid = 0 (no modeled source deductions in this tool).

The personal engine then follows the methodology documented on the Canada Personal Income Tax Calculator methodology page: it computes taxable income, federal and provincial tax, dividend gross‑up and DTC, CPP/EI, and marginal/average rates.

6. Personal Outputs Used by the CCPC Calculator

From each personal tax run, the bridge reads:

Total income tax (federal + provincial) for each shareholder.
CPP and EI contributions (implicitly included in the total burden in the personal engine).
Take‑home income after income tax + CPP + EI.

The CCPC UI surfaces a simplified summary for each shareholder: total personal tax, total burden, and net take‑home pay.

Combined Burden and Effective Rate

7. Single‑Shareholder Combined View

For a single shareholder, the bridge computes:

Tax_pers = output of personal engine (total income tax)
Tax_corp = total corporate tax (federal + provincial)
Burden_total = Tax_corp + Tax_pers
Rate_eff = \[ \begin{cases} 0, & \text{if } R = 0 \\ \dfrac{Burden\_{total}}{R}, & \text{otherwise} \end{cases} \]
NetPersonalTakeHome = take‑home income from personal engine

The effective rate is expressed relative to gross corporate revenue (R), not corporate profit. This shows the combined corporate + personal tax burden relative to the total income generated by the business.

8. Two‑Shareholder Combined View

For two shareholders, the bridge computes:

Tax_pers,1, Tax_pers,2 = total income tax for each shareholder
Tax_corp = total corporate tax
Burden_total = Tax_corp + Tax_pers,1 + Tax_pers,2
Rate_eff = \[ \begin{cases} 0, & \text{if } R = 0 \\ \dfrac{Burden\_{total}}{R}, & \text{otherwise} \end{cases} \]
NetPersonalTakeHome = take‑home₁ + take‑home₂

The calculator displays corporate results (taxable income, tax, after‑tax cash, retained earnings), per‑shareholder results (personal tax and net take‑home), and the combined totals and effective rate.

Assumptions and Limitations

Tax year is fixed at 2025; corporate and personal parameters are loaded from JSON data files for that year only.
The calculator models active business income only; investment income, passive income rules, and refundable taxes on investment income are not included.
No associated‑corporation rules or grind‑downs of the SBD limit are modeled; the small business limit is applied as‑is from the data files.
Loss carryforwards, loss carrybacks, and integration with previous or future years are out of scope.
RRSP, FHSA, and other registered‑account interactions for shareholders are not modeled; the CCPC calculator passes zero for those fields into the personal engine.
Source deductions (withholding at source) and installments are not modeled; tax paid is treated as 0 and the focus is on the structural burden rather than balances owing or refunds.
Shareholder province of residence is assumed to match the corporate province for personal tax purposes in this version.
All amounts are in Canadian dollars, and bracket thresholds and rates are taken directly from the data files; any corrections to those data sources will flow through to this calculator.
Rounding is applied at the display layer and in some bracket summaries; internal computations use full floating‑point precision.

Implementation Notes

The corporate engine calculateCorporateTax() is pure and deterministic: given taxable income and province, it returns tax and a full breakdown, including SBD limit and per‑tier amounts.
The personal engine computePersonalTax() is shared with the Canada Personal Income Tax Calculator and is validated separately via known‑answer tests.
The bridge computeCCPCTax() combines these outputs and is responsible only for mapping inputs, summing taxes, and computing combined metrics.
The “Show the Math” section on the CCPC calculator page reads directly from these engine outputs to render bracket tables and summary lines; this methodology page describes the underlying steps.

If any discrepancy is identified between this documentation and the live CCPC calculator, the corporate engine, canonical personal tax engine, and CCPC bridge (corporate.engine.js, /calculators/canada-income-tax/js/tax.engine.js, and ccpc.bridge.js) are the source of truth. This page will be updated to match them.

What This Calculator Does Not Include

Part I / Part IV refundable tax on aggregate investment income and RDTOH pools.
Associated corporations, SBD grind-downs, and complex corporate groups.
Quebec-specific corporate tax schedules beyond the encoded provincial data.
AMT, trust rules, and professional corporation governance nuances.
Real-time CRA assessments, instalments, and interest or penalties.

Sources and References

Canada Revenue Agency (CRA)
Government of Canada
Statistics Canada
Bank of Canada
CMHC (housing and mortgage context, where relevant)
OSFI (financial institution supervision, where relevant)
SPIVA Canada (long-horizon fund performance context, where relevant)
Robert Shiller — historical data (market and long-horizon data context, where relevant)