U.S. Taxpayer ID Number是指美国纳税人身份号码：

关于这个如何填写参考如下解释：

如果是独立的个体纳税人，一般来讲你的SSN就是你的纳税号，有SSN号即可。

所以只需要填写SSN即可。

对应一些在美国有业务或者生意公司的人来说，除了SSN号码，还需要一个联邦税号Tax ID number,也叫ITN。

还有一种情况会有EIN.

EIN Employer Identification Number.
TIN Taxpayer identification number.

普及知识：

 An EIN is a TIN, but a TIN is not an EIN.

TIN stands for "Taxpayer Identification Number". It is an identification number used by the IRS. There are 5 different types of TINs:

1. SSN - Social Security Number
2. EIN - Employer Identification Number
3. ITIN - Individual Taxpayer Identification Number
4. ATIN - Taxpayer Identification Number for Pending U.S. Adoptions
5. PTIN - Preparer Taxpayer Identification Number

An EIN is also know as a "Federal Tax ID Number" or "Federal Tax Identification Number". Now these are the same thing: an EIN and a Federal Tax ID Number are synonymous, although, officially, EIN is used more often by the IRS. Sometimes it will be referred to as a "Federal Employer Identification Number" too. And rarely, you may find the acronym FEIN, although is not commonly seen and the IRS does not refer to it is the FEIN. The IRS does note that the EIN is also known as a Federal Tax ID Number, but not an FEIN.

Hopefully this helps! So in short, they are not the same, but rather an EIN is a type of TIN that is used to identify a business entity (LLC, Corporation, Limited Partnership, etc).