What documents do I need from all employers
W-2 form
Key document. Sent by the employer at the beginning of the following year after working in the US - a copy is enough
Copy of last check
It is an alternative to the W-2 form, for filing. If you have a W-2, it is not necessary to but it is an advantage.
Inclusion of all work
It is necessary to include work, which the visa sponsor does not know about