In case of forgetting the Udyam Registration Number (URN), the business owner can retrieve it through the Udyam Registration portal. The portal provides an option for the business owner to retrieve the URN by entering their PAN number and the registered mobile number or email ID. Once the details are verified, the portal will display the URN, and the business owner can use it to access the Udyam Registration Certificate and avail various benefits and incentives provided by the government for MSMEs.