Business tax ID number prefixes
The Service Center of the Internal Revenue Service assigns business Tax ID prefix numbers. These prefixes are normally assigned according to the mailing address of the taxpayer, however, there are several exceptions to this general rule. These prefixes correspond to the number given to the District Office having jurisdiction over that mailing address area. For instance, a taxpayer with a mailing address of Maryland would normally be assigned a Taxpayer ID number with the prefix of 52.