Enough to cover the work the partner would have done. Price the replacement labour, add payroll taxes and recruitment time, and extend the runway for a slower ramp-up. The reserve is a planning figure, not a qualifying threshold; what matters is that committed, at-risk capital fits the enterprise's actual cost.
Reprice the plan, not just the payroll line
A departing partner often took work in several directions at once: selling, scheduling, bookkeeping, opening the premises. Replacing them can mean two part-time hires rather than one salary. Rebuild the forecast from tasks, then check whether the projected returns still support more than a minimal living or a significant economic contribution.
Keep household spending in a separate budget, and treat any capital not yet irrevocably committed as still uncommitted. Separate three pots that tend to be mixed after a partner leaves: the capital committed and at risk in the enterprise, the working reserve the business needs to reach its plan, and the household’s own living costs. Only the first bears on the qualifying investment, but running out of the second is what closes businesses.
Hypothetical example: an investor in an optical-lab equipment venture replaces a departed partner with a full-time manager and a part-time bookkeeper, which raises fixed costs and pushes profitability back two quarters; the forecast should say so rather than absorb the change silently. Money still sitting in the investor’s own account, recallable at will, is generally not irrevocably committed however firmly it is earmarked.