Most likely INS will want to see this information...
Also for a small company, they will want to see tax returns to see if the company can afford to pay your salary.
One of the main things that the INS is looking for when they process the I140 is the ability of the company to pay the salary, so you will need to get this information from the employer.
If the company is not willing to give you the information, you have have them forward it directly to the lawyer assuring them that you won\'t have access to it.
Hope this helps.