SS# = Social Security Number
In the United States, a Social Security number (or SSN) is a 9 digit number issued to citizens, permanent residents, and temporary (working) residents under section 205(c)(2) of the Social Security Act, codified as 42 U.S.C. § 405(c)(2). The number is issued to an individual by the Social Security Administration, an agency of the federal government. Its primary purpose is to track individuals for taxation purposes. In recent years the SSN has become a de facto national identification number. A social security number may be obtained by applying on Form SS–5, "Application for A Social Security Number Card" (see 20 C.F.R. sec. 422.103(b
An Australian Business Number, or ABN, is an 11 digit unique identifier issued by the Australian Taxation Office that is used by business entities when dealing with the Australian government. It was introduced as part of the New Tax System brought in by John Howard's Liberal government on 1 July 2000 as part of the Goods and Services Tax.
Corp ID# could also be an EIN is a unique number the IRS gives to businesses (including sole proprietors), government bodies, churches, trusts
and estates for tax identification purposes. EINs have two digits, a dash and then seven more digits (e.g., 75-6948657).
The ABN is an eleven digit number where the first two digits are check digits. Unlike with the TFN, the ATO has publicised the formula for checking and creating valid ABN checksums. Also, the nature of the ABN algorithm means that any 9 digit number can be made into a valid ABN.