During the offer negotiation, before the shareholding is documented. Once share certificates are issued and an agreement is signed, changing the arrangement involves corporate and tax consequences that did not exist while it was still a proposal.
Raise it while everything is still a draft
The sequence that works is: understand the proposed equity, get immigration advice on it, then let corporate counsel document whatever the parties agree. The sequence that causes problems is the reverse, where the equity is executed as part of a compensation package and the immigration question surfaces weeks later when a support letter is being drafted. By then the applicant is asking a company to redo completed work.
Where an arrangement has already been executed, it can still be reviewed and sometimes adjusted, but the cost and the awkwardness are higher. Build several weeks into the plan for this, and do not commit to a start date until the analysis is complete. Hypothetical example: Kofi is a marine-navigation software analyst whose U.S.
start date is tied to a product launch. She should begin with a dated checklist: citizenship proof, profession evidence, credential records, the employer letter and every ownership document. The shareholder agreement and board consents determine whether a proposed grant can be resolved before the requested start date.
He should obtain immigration advice before shares issue, then let corporate counsel implement any agreed change, and only then request admission or use the employer petition process. The usual failure is scheduling travel around a launch before a control issue is known. A Canadian can request TN admission at an inspection location; an employer may instead file I-129 with USCIS.