If the person is currently working on H-1B visa for one employer (or has worked in recent past), and when such person changes to job to another employer, that another employer has to file new H-1B petition for the employee. Many people, including some immigration attorneys, call this process an "H1 transfer". Even in this document, we refer to the new petition by new employer as "H-1B transfer", solely for the ease of describing. It is very important to understand that there is really no concept of "transfer". Nothing gets transferred from one employer to another employer, except the employee itself. Previous employer does not have to "transfer" something to new employer, previous employer does not even have to know about the new employer.

Therefore, when people say "H1 transfer", it is actually just a new H-1B petition, all over again, without the restriction of H-1B cap.

When the new petition is filed by a new employer, it may generally be with a request to extend H-1B status. As nothing gets transferred, neither the new employer nor the employee need to take any permission from the previous employer to file new H-1B petition.

In order to file a new petition with the new employer, in addition to the regular documents needed for filing the H-1B petition, you will also have to submit the following additional documents:

• Two or three most recent pay stubs.
  
  
• Copy of your most recent H1-B approval notice, Form I-797
  
  
• Copy of all pages of your passport (including blank ones), which is valid for your entire requested period of stay in the U.S.
  
  
• Photocopy of Form I-94. Do NOT send the original. You are not required to send the original. If you sent the original by mistake, and if you need it back, you can file form G-884 with USCIS. G-884 is not available online. You have to request it by mail.
  More details.
  
  
• Copy of the most current visa stamp. Visa stamp does not have to be unexpired.
  
  
• Latest resume.
  
  
• Copy of social security card.
  
  

• After the new employer files for an H-1B transfer, you can start working for the new employer as soon as you get the receipt notice.
  
  
• If you previously worked for employer A, and now have a pending H-1B petition for employer B and if you would like to now work for employer C, you can do that as long as employer C files new H-1B petition for you, as long as you are in status.
  
  As there is really nothing getting transferred from A to B to C, you don't have to necessarily get petition with employer B approved first. If you already started working for employer B after receiving the receipt notice and before it being approved, and if you would like to work for employer C, the petition from employer B must be approved in order for the petition from employer C to be approved as an extension of status.
  
  
• If you were either on bench or you were otherwise not paid while previously employed, it is still possible for a new employer file H-1B petition for you, even if you don't have recent pay stubs. As there is no concept of transfer, it is still possible that the new petition be approved. However, in absence of recent pay stubs, if you failed to maintain the valid H-1B status, it may not be possible to obtain and H-1B extension of status within the U.S. USCIS may instead ask you to go back to your home country and ask him/her to reenter on new Form I-94. If your visa stamp has already expired, you will have to get your visa stamp at the consulate before being allowed to enter into the U.S. again.
  
  
• In case you had an approved H-1B petition from an employer, but never worked in the U.S. because you never entered the U.S., it is still possible for the new employer to file new H-1B petition for you with any new paystubs. As there is really no concept of transfer, this is not even an issue. You will not be subject to H-1B cap. You don't require any paystubs because, if you are not in the U.S., the extension of H-1B status is not even applicable. You will be issued Form I-94 when you enter the U.S.
  
  Also, if the current visa stamp itself has not expired, you don't need new visa stamp.
  
  
• More information can be found in H1 transfer FAQ.