The contract terms that keep direction and supervision with the petitioner, and evidence that the placement is work requiring the employer's specialised knowledge rather than the supply of labour. The services agreement, the reporting structure and the ownership of the deliverable are the documents that answer it.
Control is proved in the contract, not in the intention
Offsite placement is where otherwise strong L-1B petitions come apart, because the statute added conditions specifically for it and a file that ignores them reads as if nobody noticed. Two things have to be untrue: that the unaffiliated company principally controls and supervises the employee, and that the arrangement is essentially one to provide labour for hire. Hypothetical example: an off-grid power installer near Saint-Joachim-de-Shefford places a commissioning specialist with an American developer for eighteen months, billing hours at a monthly rate against timesheets the developer's site manager signs.
Every visible feature of that arrangement points the wrong way. The same work can often be structured to point the right way, and it must be genuinely restructured rather than merely redescribed. Assign work through the petitioner's own project lead.
Define deliverables and acceptance criteria rather than hours. Keep performance review, discipline and replacement decisions with the employer. Bill for a defined scope.
Then attach the agreement showing those terms, because an officer will read the contract before reading the assurance.