The USCIS defines a work permit as an Employment Authorization Document (EAD). While most people believe that this is a work visa, this is not necessarily the case. Most employers need to see an EAD card before hiring someone. An EAD card shows that you are qualified to work in the US. To qualify for an EAD, you need a document to prove that you can work in the US. This can be any document that authorizes you to work in the US. It can include a visa, but it can also include a green card or other documentation. It is important to secure an EAD before seeking work in the US.
Employers are required to confirm that you have a permit to work in the US before hiring you. This is because employers who hire an undocumented worker (a worker without a work permit) can face severe penalties and punishments. Even if you are in the US temporarily, you may be able to apply for a work permit, depending on your specific situation. Check the USCIS website to see whether you qualify for US employment. Or, speak to a qualified US immigration attorney to find out what the best process for you is in applying for a work permit.
If you qualify to work in the US but are not a green card holder, conditional resident, or US citizen (in which cases you do not need additional proof of work permit), you can apply for an EAD or work permit by competing and submitting USCIS Form I765. If you have a green card, US citizenship certificate, or proof of conditional residency, you do not need a work permit. Your evidence of your status is enough to qualify you for work in the US. Similarly, if you are authorized to work in the US for a foreign company or government, you will not need a work permit to work in the US. In this case, your Arrival/Departure Record (Form I-94) and passport will prove your work eligibility. If you have an H4 visa, you will need to apply for I-485 first, before obtaining your permit for work.
If you apply for EAD, you will need your actual EAD card before you officially have your work permit and begin working in the US. Therefore, apply for your EAD card as soon as you realize you will need a permit to work in the US.