USCIS announced that as of October 3, 2017, it has resumed the premium processing for all H-1B petitions, including the conversion of pending petitions. On September 18th USCIS resumed premium processing of H-1B petitions subject to the cap and on July 24th it reinstated premium processing for H-1B petitions filed by cap-exempt petitions based on the Conrad 30 Waiver program and interested government agency waivers.
Premium processing expedites the adjudication of a petition and USCIS is required to provide a decision or request additional evidence within 15 calendar days. If it fails to meet this deadline then it must return the premium processing fee.
Premium processing is particularly important for the beneficiaries of pending H-1B extension petitions, since they are only granted 240 days of continued employment authorization after the expiration date of their most recent H-1B approval notice. They are allowed to remain in the US after this 240-day period if the H-1B extension petition was filed before their H-1B status expired, but their employment authorization terminates after this period.
It is not necessary for an H-1B petition to change employers to be approved before the beneficiary may work for the new petitioner. The beneficiary may work after USCIS receives the H-1B petition from the new employer pursuant to portability.