Ask How do I handle multiple accounts from the same user in membership site?

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I'm building a membership site and need help. Users are creating multiple accounts. I'm using a basic system now. It doesn't track duplicate users well. I've tried checking email addresses, but users can use different emails. I've also looked at IP tracking, but it's not foolproof. I need a better solution. How do I effectively handle multiple accounts from the same user in my membership site?