Forms can help you and your tax preparer understand what you have to report and ensure a complete account. Forms and certifications are necessary if you do not have a tax filing requirement yet. The IRS needs only information about you to prepare your taxes and other transactions. You. The TIN is a number used to identify the taxpayer (or individuals) in a financial transaction. Most transactions are reported to your tax return, with tax breaks for various situations such as retirement savings plans or home equity loans. A W-9 must be used to provide information to the IRS in response to its request. The W-9 forms help you with completing your IRS tax return, which is needed for all major transactions. However, this form. A customer, such as a business, needs this form to report certain income from a particular activity. As part of that activity, the customer makes a purchase or services under circumstances which raise questions about its status as a tax collectible item. In addition to information about transactions, the forms give information about the source of income or the business operations of a company. Information about whom a customer is, the nature of business activities, and the nature of transactions can help you. This form provides the IRS with information so the requester (usually a corporation, partnership, organization etc.) can determine the taxable status of the company. The TIN of the individual paying the payment does not determine the amount of income or expenses involved. The W-9 forms must be completed at least three weeks after the day of the original tax transaction. Forms may be faxed and returned within 5 days and signed and completed by the requester and notarized. The customer can choose to be listed as an optional taxpayer within the account file and will be required to file a copy of the return.