With the instrument that created the entitlement, the payer's statements for the whole period relied on, the tax returns reporting the income, and an unbroken bank record carrying each payment from receipt through to the enterprise. Recurring income needs more paper than a single sale, not less.
Recurring income means recurring proof
A lump sum has one story. A stream of payments accumulated over years has a story for every payment, and applicants underestimate how much of it has to be shown. Start with the source of the right itself: the royalty agreement, lease or settlement that created the entitlement, together with whatever established the applicant's ownership of the underlying interest in the first place.
Then show the payments arriving, matched against the payer's own statements. Then show them declared, because tax filings that do not reflect the income undermine the lawfulness of the source rather than merely leaving a gap. Hypothetical example: an applicant near Saint-Joachim-de-Shefford accumulated a quarterly royalty from an aggregate pit across eleven years, in an account he closed after switching banks, and can retrieve only the last three years of statements.
Request archived records early, because institutions charge for old statements and take weeks to produce them. Where a genuine gap cannot be closed, say so plainly and evidence the surrounding period rather than presenting an incomplete run as though it were complete.