When starting a business, one of the first things you must do is apply for a federal identification number. Then, for each employee you hire, there are several forms they must complete. You can find them all here, available in downloadable PDF format.
SS-4, Application for Federal Identification Number — Regardless of your business structure (corporation, partnership or sole proprietor), you'll need a federal identification number to begin. This number is used when paying employment taxes on behalf of your employees. The completed Form SS-4 may be sent to your local IRS office via mail, fax or even called-in. Download Form SS-4 (External PDF).
I-9, Employment Eligibility Verification — Each employee you hire must complete this form and provide supporting documentation. It is your responsibility to keep this form in the employee's file. Download Form I-9 (External Link).
W-4, Employee's Withholding Allowance Certificate — Every one of your employees must provide you with a signed W-4 to indicate the number of withholding allowances to use when calculating their Federal Income Taxes. If employees wish to change their allowances, they must submit a new W-4 to you. If a W-4 has not been submitted, employers are required to withhold taxes at the highest rate — single with 0 allowances. Download Form W-4 (External PDF).