Entry and exit records, prior passports with their stamps, employer travel and expense records, payroll data showing which location paid the person, and airline or hotel records for the relevant periods. The evidence has to establish physical presence outside the country on specific dates, not merely that travel happened.
Build the record while it still exists
This is the part of the file most likely to fail for practical rather than legal reasons. Employers purge expense systems, airlines retain booking history for a limited period, and a previous employer has no obligation to help a departed employee reconstruct anything. Anyone who may want to rely on time abroad should begin gathering records before there is a petition to attach them to, and should keep prior passports rather than surrendering or discarding them when they expire. Personal calendars, immigration entry histories and even bank card transactions in a particular country can corroborate a timeline. Present the reconstruction as an organized schedule with each period supported, rather than as a folder of receipts, and have a licensed adviser assess what the total actually supports.
Corporate documents should be assembled in a sequence that lets an independent reader follow ownership, operations, and the beneficiary's role without guessing. The personnel record must then establish the qualifying foreign employment and the seniority of the proposed U.S. position. A transfer normally requires twelve uninterrupted months with the related foreign organization in the relevant three-year period, and L-1A cannot exceed seven years in total. Hypothetical example: A recycled-glass manufacturer has changed holding companies twice. The decisive records are share ledgers and transaction documents that show the relationship continued, rather than an organizational chart created for the petition.