If the owner is not listed in a payroll document or your quarterly wage report, they will ask for your past year tax documents to make sure you are eligible.
Some, but not all, carriers have restrictions against companies that consist only of owners. So even if the owner is listed in the wage report or payroll, some carriers will still ask for your tax documents to make sure your company is not an owner-only group or to verify exactly who is an owner.
The tax document the carriers request is dependent on how your company is structured.
C-Corp: First 4 pages of Form 1120 + Schedule G
S-Corp: Schedule K-1
LLC: Schedule K-1
Single Owner LLC: Schedule C
Sole Proprietorship: First 4 pages of Form 1040 + Schedule C