Taxpayer Numbers
Individuals need a taxpayer number in order for the annual tax return to be fully processed. The IRS will accept a tax return showing Applied For in the taxpayer number space. Once the taxpayer number is received, it should be sent to the IRS to match with any temporary numbers used to complete processing. The IRS will not send a refund for any tax overpayment on a return with no taxpayer number.
Whether a crewmember applies for a social security number (SSN) or an individual taxpayer identification number (ITIN) depends upon potential work authorization. A person on an L-1 will have potential work authorization. Crew holding other visas such a C1/D or B1/B2 will not qualify for an SSN so will apply for an ITIN.
The application for an ITIN should be submitted with the tax return when filed unless an exception applies. The only relevant exception would be when the compensation is expected to be exempt under a tax treaty. In those cases, the ITIN application is submitted along with Form 8233. See Crew Payroll Taxes for more information on the treaty exempt wage process.