In general, the company asking you to complete Form W-9 has made a payment to you and is likely required to file an information return with the IRS to report this payment. Form 1099-MISC is an example of an information return. In order to complete the information return and communicate your identify to the IRS the company will need to obtain your Taxpayer Identification Number (TIN). The IRS has created Form W-9 as the process for companies to obtain TIN numbers from those they are making payments to.There is no deadline to complete a Form W-9. However, companies are required to withhold 24% of any payment and remit it to the IRS if you do not prthem with a completed Form W-9. Therefore, most companies will hold payment until they receive a complete Form W-9 in an effort to avoid withholding 24%.For more information on the Form W-9 process see https://www.w9manager.com.