What a gross-up does, conceptually
Rather than itemizing and documenting individual add-backs one by one, a gross-up simply inflates reported net self-employment income by a flat percentage, on the theory that a self-employed person's real cash-flow capacity typically runs somewhat ahead of their taxable income after legitimate deductions.
The published figure to know
CMHC's mortgage loan insurance program allows self-employed sole proprietors or partnerships to have their self-employment income grossed up by 15%, as an alternative to the itemized add-back approach from Module 04. In practice, a lender or broker generally applies one method or the other on a given file — not both at once, which would double-count the same underlying adjustment.
Why this is a sole-proprietor tool, not an incorporated one
The 15% gross-up applies to sole proprietors and partnerships specifically because their personal income figure already is the business's whole result. It doesn't extend automatically to incorporated owners, whose personal income is simply whatever salary or dividends they chose to pay themselves — a number that's already somewhat controllable. Grossing that figure up doesn't answer the real question for an incorporated file, which leans instead on ownership percentage (Module 11) and the corporation's own results.
Other insurers, other methods
Canada Guaranty's Low Doc Advantage program for self-employed borrowers instead assesses stated income on a documented "reasonability" basis against the nature, size and tenure of the business, rather than publishing a fixed gross-up percentage — the same underlying goal as CMHC's approach, reached by a different published method. Treat any specific insurer figure or method as a snapshot worth reconfirming before quoting a client, since these programs are updated over time.
A worked example
A sole-proprietor plumber with a two-year-average Notice of Assessment line 15000 figure of $52,000 would qualify, under the 15% gross-up, on roughly $59,800. Under an itemized add-back approach, if documented CCA and business-use-of-home add-backs total a similar amount, the two methods often land close together — which is really the point: both are trying to close the same gap between taxable income and real cash-flow capacity, just by different routes.