Once you cease employment with your H1B employer, your H1 status effectively ends as well, and the employer is obligated to report the termination of H1 employment. You can port an H1B (i.e., begin work with the new employer while the change of employer petition is pending with USCIS) only if you filed for the change of employer while on a "currently valid H1B" and you would need to show a recent paystub to prove the currency of the old H1B. In your instance, you would not be able to port the old H1 and would need the new H1 to be approved before you can start employment with your new employer. If you filed under premium processing, you should get an answer within 15 business days and so could start very soon anyway. All the best.
Elizabeth C. Surin, Esq.
It doesn't matter if the same employer is filing the H after you changed status to an H4. After you convert to another nonimmigrant visa, you will need to wait for the H1 petition to be approved even if you previously worked in H status for the same employer who now needs your services. In your case, you can't start working until October 1, 2010 anyway since no H visas are currently available - even if you are premium processing and did not do 6 years in H status.
There are two main issues you need to consider.
First, you are eligible to benefit from the H1B portability provisions. This means that you may commence your employment upon the filing of the new H1B petition. If you utilize the premium processing service, you will receive an email receipt notice within 2 days of the receipt by the USCIS and you will receive either an approval or request for evidence within 15 calendar days of filing.
Second, as a general matter paying the $1000 premium processing fee is worthwhile. This way you will have a decision in 15 calendar days from the date of filing instead of 2-4 months from the date of filing. The peace of mind of having the approval is worth the fee and knowing that your employment will not be interrupted.
Feel free to take advantage of our Free 30 Minute Consultation to get the reliable advice you require. You can schedule your appointment by clicking on the BOOK NOW button on our website: www.glinlaw.com and choose Option 1. The link below will also take you to the appointment scheduling system. We would be happy to work with you so that you can make an informed decision on how to proceed.