You can create accounts for your referrals using Udimi affiliate API.
To start using API, you have pass identity verification and earn a commission as a Udimi affiliate.
Using access token and HTTP request, you can create accounts for new users. You'll have to provide user's full name and email.
After creating the account, it will have "Unconfirmed" status. The referral will have 72 hours to confirm it in the email that he'll receive from Udimi.
After confirmation, you'll see a new referral in your Referral API generator stats and it will be displayed in general Affiliate stats.
Pay attention to the expired accounts rate. If a lot of referrals don't confirm the accounts that you create for them, access to API can be blocked.