Any management services agreement or engagement contract, the invoices and payment records, corporate minutes describing the role, tax filings for both the individual and the personal corporation, and whatever payroll records exist for any period of direct employment.
Assemble the whole history, including the inconvenient parts
Give counsel the complete picture rather than a curated version. That means the agreements, the invoices, the corporate resolutions appointing the individual to any office, and the tax treatment on both sides, because the tax treatment often reveals how the relationship was actually characterized. If there was an earlier period of straightforward employment before the arrangement changed, its payroll records matter a great deal, since the qualifying year has to sit inside a three-year window and an earlier period may or may not fall within it. Where documents are missing, note the gap rather than describing what you believe they would have said. A partial record that is honest is far easier to work with than a complete one that is reconstructed.
Hypothetical example: Philippe is moving from a dental-laboratory chain to its American affiliate, but the Canadian entity changed its name after a reorganization. An opening assessment matches the old and new legal names, ownership records, and payroll history. Corporate filings, share records, tax records, and board resolutions settle whether the foreign employer and petitioning group have the needed relationship. Assemble them chronologically, with a one-page ownership explanation, before drafting the petition narrative. Trouble follows when invoices or letterhead use one entity while payroll uses another and no document links them. A precise corporate timeline is more persuasive than repeating that the companies are related.