The letter should accurately describe the proposed employment and relevant assignments under the applicable procedure. Explain material customer-site or intermediary arrangements and provide supporting records where needed. Do not combine separate employing arrangements into one letter merely to make the file appear simpler.
Use a project schedule with supporting agreements
List the proposed duties, locations and dates and connect them to the responsible employer. Reconcile differences between the schedule, offer and contracts. Keep the professional qualifications in the file as well; an accurate itinerary does not itself establish that the work fits a listed profession.
Build the file from contemporaneous records: a detailed employer letter, agreement or offer, itinerary where useful, credential evidence and proof tying the signer to the engaging entity. The first review should produce a gap list, such as an unexplained customer site or different dates in the statement of work and offer. Resolve those gaps before asking an officer to infer the arrangement.
Hypothetical example: A Canadian zoologist is hired by an Arizona wildlife-management company to assess habitat impacts at three ranches. Her letter says she will work for the ranches, while invoices show the company pays and directs her. The company contract, payroll terms and project schedule can settle the employment structure if they are described consistently.
A common mistake is attaching every document available without explaining who is responsible for the services; volume does not repair a contradictory record. Prepare a final consistency check using names, dates, title, compensation, location and duties. The review should identify one authoritative record for each fact.
If a customer requires a different project title, explain that difference directly instead of letting two titles suggest two separate jobs.