I need to set up a new vendor record, however, the IRS Form W-9 lists two different names (Line 1 Taxpayer Name and Line 2 Business/Disregarded Entity Name). Which name should I use to create the vendor record?

Either name can be used for the vendor record, but it must match the name of the entity or individual you are doing business with (i.e., the vendor record name should match the name that appears on the quote, invoice, contract, wire/check payment, etc.).