Use a truthful chronology with actual employers, duties and dates.
Preserve the transition rather than backdate it
Describe what knowledge came from each period and what work occurred after joining. Do not relabel customer-side employment as company employment merely to lengthen the qualifying period.
Prepare a dated chronology that names each legal employer, work location, pay source, title, and set of duties. Support the customer period with service contracts, purchase records, or access logs, and the employee period with payroll, tax, personnel, and internal assignment records. A transition letter may explain why the company recruited the applicant, but it should not move the hire date backward. The petition must prove a continuous qualifying year abroad within the applicable prior three years and a qualifying relationship between the foreign employer and US petitioner. Evidence of specialized knowledge should identify the company product, process, or procedure involved and explain why the later employee’s understanding is advanced or special, rather than merely showing long industry experience.
Hypothetical example: An industrial-kiln controls specialist from Rivière-Éternité first calibrated equipment for a purchaser and later became an employee of the controls maker’s affiliate. Her chronology uses customer work orders for the first phase and payroll plus internal engineering assignments for the second. A supervisor confirms the exact hiring date and describes knowledge gained afterward without backdating employment. Corporate records establish the affiliate relationship. This division preserves useful earlier experience while making clear which months can count toward the statutory foreign-service year.