Given this year's cap has been reached, when can I submit an H-1B petition for the upcoming year?

New H-1B visas are issued annually in October. So the next set of H-1B visas will be available in October. However, applications for H-1B visas for the upcoming visa year may be filed as early as April. Applicants must select an H-1B start date no earlier than October 1, the date that visas become available. Such applicants may begin work upon the approval dates of the H-1B visa but no earlier than October 1.