Is there a dollar threshold below which an estate trustee doesn't need receipts for small expenses?

No, there's no set dollar threshold under Ontario law below which an estate trustee is excused from keeping receipts. The general expectation is that a trustee accounts for every dollar of estate money spent, however small, and that expectation doesn't come with a built-in exemption for minor purchases.

In practice, courts and beneficiaries reviewing a passing of accounts tend to be reasonably pragmatic about genuinely small, incidental costs where a receipt was never realistically available, such as a modest cash tip for movers, but "reasonably pragmatic" isn't the same as a guaranteed pass. A trustee who can't produce documentation risks having that item questioned or disallowed, and a pattern of consistently unreceipted expenses, even small individual ones, looks very different to a court than one or two isolated gaps in an otherwise well-documented accounting.

Because there's no safe dollar cutoff to rely on, the practical approach is to keep a receipt or at least a clear written note, covering what it was for, the amount, and the date, for every estate expenditure, no matter how minor it seems at the time, rather than assuming small amounts won't be scrutinized.