Most organizations to which you sell your goods or services will assign you a unique vendor number. For instance, if Macy's sells your fashion line, the company will enter you into its vendor database and assign you a vendor number. There are a few things you need to know if you want to get a vendor number with any particular business, non-profit organization or government operation.

Most companies, when they enter you in their vendor database, will require your IRS-assigned employer identification number, sometimes called your federal tax identification number. If you're a sole proprietorship, your Social Security number should be sufficient. However, in addition to being the more commonly accepted identification number for getting a vendor number, having an EIN also helps protect you from identity theft. The IRS offers an online service where you can apply for an EIN and have it issued immediately (see Resources).

The companies you do business with will issue you a vendor number that's often your EIN with a few extra digits tacked on. Use that number on all the invoices or any other correspondence you send to this business or government agency.

If you want to do business with state or local governments or federal government agencies, find out what their vendor registration procedure is. Frequently you have to enter data into their online databases yourself, and only then you can bid on their contracts.

Don't assume that if you have a vendor number with one government agency, it will be the same for other parts of the same government. Likewise, having a vendor number with a department store branch or a fast-food franchise location is often good for that location only, and you need to get a separate vendor number for each franchise location or store branch with which you do business. There are some state governments that have tightened up this process by implementing state-wide vendor databases.