The User Registration Invite Codes add-on restricts registration on your site to users who have invite codes only. You can create a single or multiple invitation codes, set an expiry date, and set a usage limit per invitation code, among other things. You can also generate a large number of random invitation codes. This is very useful if you need to create multiple codes.

WPC Smart Linked Products
Boost your online store’s sales with WPC Smart Linked Products. Easily recommend upsells and cross-sells to your customers, increasing average order value and enhancing their shopping experience.