Capital Gains tax on Spanish Stock US Resident

I am planning on selling the shares but i have read some stuff about having to file a spanish (sic) 210 tax form. Do I have to do that? I am not a spanish (sic) resident and have never lived or worked in spain (sic).

Yes, chances are you should do. But hopefully enough, chances are you might not need to, as a particular exception on being a US national (but sadly I can't quote properly about this).

In case you actually have to fill modelo 210, failure to comply could be fined up to 200EUR, on a case of article 198 of the "general taxes law" of Spain. Note that this is because you haven't had net income on the operation. If you haven't had net loss on the operation, you would be subject to a case of article 191 of the same law instead, which is a proportional fine.

Here's your help page for modelo 210. This is the law ultimately governing over all of your 210 stuff (but there are many more).

Hope that helped.

_{DISCLAIMER: This is not your tax advisory, it's a vague (yet informed) entry level reference in order to guide you. Here's no responsibility for any damages caused. If on doubt, always choose to go to the tax advisory office or to the revenue service office, depending on the cases.}