After the ownership documents are in order, the qualifying year is evidenced and the US operation is genuinely ready for the transferee, and with enough margin before the intended start for a request for further evidence. In a seasonal business the quiet months are usually the practical filing window.
File on the strength of the file, not the season
The most common scheduling error is choosing a filing date from the operational calendar and then trying to make the evidence arrive in time. Reverse it. Fix the date the corporate and payroll evidence will genuinely be complete, add a realistic allowance for questions from the agency, and only then discuss a start date with the people running the American operation. Nobody should begin performing productive work in the United States before the classification exists; travel for permissible business activity is a narrower allowance than most business owners assume and should be assessed against the specific tasks intended. If the transfer cannot be ready for the season everyone had in mind, the honest response is to plan the following one properly.
Hypothetical example: a farm-equipment remanufacturing managing director is expected to take over during a plant expansion, but a shareholder reorganization will close two months later. A first review asks which ownership structure will exist when the petition is filed and preserves signed closing documents once it does. Filing against a chart that will immediately be obsolete invites avoidable questions. Work backward from stable ownership, complete foreign payroll evidence and the U.S. role description. The transferee should not begin managing the American operation before the classification has been approved.