Meet QR code automation rule and Scan QR code trigger in your Bitrix24 CRM. These tools can help with event attendance tracking.
At the first stage of the deal, add the Create QR Code and the Send email/Send SMS automation rule (here is how
If you invite only contacts from your CRM, then create a deal with a sales generator.
If you want to attract new people, place a CRM form on your website.
Add the Scan QR Code trigger. Your event managers will be able to scan guests codes at the entrance. After scanning the code and confirming that the guest has actually attended the event, the trigger will move the deal to the specific stage.
With this script you can see who have actually attended the event and who haven't (more about the script here).