The rule of thumb is that a reference letter must contain the company's letterhead. However, if your past company doesn't have any letterhead there is not much you can do about it. Here's my two cents,
1) Get a notarized letter mentioning all the reference letter details signed by your immediate supervisor/ HR/ Colleague
2) Try to get your supervisors business card
3) Pay stubs, salary certificates, offer letter, and any other relevant documents proving you've worked for them
4) Last but not least, Email from HR that they don't have a letterhead for the company.
The rule of thumb is that a reference letter must contain the company's letterhead. However, if your past company doesn't have any letterhead there is not much you can do about it. Here's my two cents,
1) Get a notarized letter mentioning all the reference letter details signed by your immediate supervisor/ HR/ Colleague
2) Try to get your supervisors business card
3) Pay stubs, salary certificates, offer letter, and any other relevant documents proving you've worked for them
4) Last but not least, Email from HR that they don't have a letterhead for the company.