Tax ID refers to identifiers like Employer Identification Numbers (EIN), Federal Employer Identification Numbers (FEIN), or Taxpayer Identification Numbers (TIN), which are issued by the U.S. Social Security Administration (SSA) or Internal Revenue Service (IRS) for tax returns and other tax-related documents.
National ID refers to country public unique identifiers (UID), such as value-added tax identification numbers (VAT) for countries of the European Union, that are issued both for tax purposes and to recognize the identifying details of the business entity to which the ID has been allocated.