Considering ExtPay but how do I know if a customer is from EU (because of VAT)?

[hckiang]

I'm located at EU and I understand that ExtensionPay doesn't support Stripe's tax functionality yet. Let's say I sell for USD $10 no matter where they're from, i.e., I give up collecting VAT dynamically according to country...

Then I'll still absolutely need to know who is from EU and who is not because once a year I'll need to tell Uncle Sam how much revenue is VAT taxable--for each EU customer the tax agency wants 20-ish percents of sales value and for each non-EU customer he'll leave that alone.

I suppose you have the same problem in the US as well. Do you just tell Uncle Sam all your customers ought to pay VAT so at the end of the year you'll end up over-paying tax? Or how do you manage this?