According to the USCIS:
U.S. Citizenship and Immigration Services today announced that the initial registration period for the fiscal year (FY) 2021 H-1B cap will open at noon Eastern on March 1 and run through noon Eastern on March 20. During this period, prospective petitioners and representatives will be able to fill out prospective petitioner and beneficiary information and submit their registrations.
A confirmation number will be assigned to each registration submitted for the FY 2021 H-1B cap. This number is used solely to track registrations; you cannot use this number to track your case status in Case Status Online.
Prospective H-1B cap-subject petitioners or their representatives are required to use a myUSCIS online account to: 1) register each beneficiary electronically for the selection process and 2) pay the associated $10 H-1B registration fee for each registration submitted on behalf of each beneficiary. Prospective petitioners or their representatives will be able to submit registrations for multiple beneficiaries in a single online session. Through the account, they will be able to prepare, edit and store draft registrations prior to final payment and submission of each registration.
If USCIS receives enough registrations by March 20, we will randomly select registrations and send selection notifications via users’ USCIS online accounts. We intend to notify account holders by March 31, 2020.
An H-1B cap-subject petition may only be filed by a petitioner whose registration for that beneficiary was selected in the H-1B registration process.