@shantu sab To my knowledge 6 years is the maximum you can have for H1B and you will need to leave the US for at least one year to be eligible for another 6 years. However, your employer can file for an extension if they have an approved labour certificate or I 140 for you and can not file I 485 due to retrogression. I think they can also file for the H1B extension if the labour certificate/I 140 is pending for more than a year. I will suggest you consult an immigration lawyer for accurate information.