Everyone needs a tax ID to work in the US. Whether you are just starting a new job, or starting a business, this is what you need to know about applying for a tax ID.

With Your SSN: In most cases, you will use your social security number as your Tax ID filing number. Your social security number will stay with you throughout your life, and you will need to use that number for taxes and to verify work eligibility. If you have forgotten your social security number- you should check your documents for your social security card or your tax documents from the last tax season.

Without Your SSN: If you are working in the United States, but do not yet have a Social Security Number, you will need to submit a Tax ID application for an ITIN or Individual Taxpayer Identification Number before you begin working. Your ITIN is used in lieu of your SSN for tax purposes. In some cases, your employer will help provide an ITIN.

For a Business: Much like individuals, all US businesses need a tax identification number. For businesses, this is referred to as an EIN or Employer Identification Number. To obtain an EIN, you will need to submit Form SS-4 either online, by fax, or by mail. Submitting the from online is the fastest method as it will only take a few days to receive a response- as opposed to several weeks that are required for a reply for faxed or mailed applications.

Having your Tax ID is definitely an essential part of working and filing taxes in the U.S. If you are applying, keep in mind that the number may take some time to process into the IRS records- about four weeks for the EIN- so you should make sure to submit the application with plenty of time before tax season.