Under ITA s.2(1) tax is charged on the income of a person, not a household. There is no joint return in Canada, and a salary cannot simply be assigned to whichever partner is in a lower bracket.
What the engine does
Each person in the plan is taxed on their own income, from age 18 to 110.[1] A plan with someone outside that range is rejected rather than approximated. Each has their own:
- federal and Ontario brackets
- basic personal amount, including its phase-out
- CPP, CPP2 and EI ceilings, see CPP and EI contributions — each person gets a full set, which is why two people earning $60,000 each pay more in contributions than one person earning $120,000
- Ontario surtax and health premium
Only the resulting net amounts are pooled, in the cash the plan spends.
The one credit that crosses persons is the ITA 118(1)(a) spousal amount, claimed by the higher earner when the other's income is low enough, federally[2] and in Ontario.[3] Only one person claims it, and not together with the eligible-dependant amount.[4] The engine can claim it, but only when a plan carries household facts, and All the Numbers does not send them. A plan from All the Numbers therefore includes no spouse amount. See age, spouse and caregiver credits. The same missing facts are why children's benefits are absent.
What it deliberately does not
- Pension income splitting (ITA 60.03), which lets a couple move up to half of eligible pension income after 65. This is the big one for retired couples.
- Spousal RRSPs, where the higher earner takes the deduction and the lower earner is eventually taxed on the withdrawal.
- Prescribed-rate loans between partners.
Each of these could lower a real couple's lifetime bill, so the projection is the figure you would pay without planning for them.