The answer to this question is found in IRS publication 1281 starting at page 5. You will receive notice from the IRS regarding an incomplete 1099. From there, you must submit a Form to the Payee. If you are continuing to pay the payee, and the payee does not provide a TIN, then above $600.00 annually, you will have to start withholding tax from the payee. Basically, it's a big headache if you have a regular 1099 payee who is earning above $600.00 annually. Hope this helps.
