|Pro Tip: How to Deal With Duplicate Adsense Accounts|
This is something a lot of people have had troubles with and yet it is one of the easiest things to sort out for yourself. No obviously, if you can delete the duplicate account yourself you should do so and you can find out how to do just that here "How To Permanently Delete a Disapproved Adsense Account" but for those people who can't just read on...
First of all its important to get to the bottom of why this duplicate account has happened in the first place. If you are trying to game the system after being banned you can forget it. Unless you turn into an entirely different person (Pro Hint: or someone you know with bank details) none of the advice in this post will help you. If that is the case I would stop trying and give up now. But if you made the older Adsense account by accident and never used it here is what you need to do.
Understanding the Link
The first thing to understand is how Google knows you have that other account. This is not an account they have made up just to annoy you, it is linked to something you own or are trying to connect with. The only way to stop Google from picking up on this duplicate Adsense account is to separate the Youtube channel or blog into a new account. You do this by first making up a new e-mail account and then transferring everything you want to connect to Adsense into that new email account.
You do this by changing channel owners & managers. You first need to add the new email account, then once you have done that you need to remove the old email managers. But then is the most important thing, to make sure NOTHING links to the older Adsense account. Nothing in contact information, nothing in permissions, it needs to be a clean sweep. Only then can you start up a new Adsense account.
Please note, that this will only work if you have not verified your Adsense account with your own personal data. If you have done that the only way to get around it is to break the link that is causing the problem and then become someone new. This, of course, is impossible and against Adsense policy, but transferring ownership isn't. I hope you get what I am getting at here.
This solution is not going to solve everyone's problems, but it should solve a lot of peoples main issues regarding this well-known problem. If you are having any issues with this or anything else Adsense related do let me know in the comments below and I will be happy to help if I can.