They need to click the dropdown and select their country from it. If it's not there then add it to the XML file below.

/components/com_comprofiler/plugin/user/plug_cbpaidsubscriptions/xml/edit.front.invoice.xml

I'm not sure I understand your reply. The country, city, etc.. is all user supplied so they can of course change as not all users are from the same location. If you want to apply a tax to everyone, regardless of location, you can do so by not having the CBSubs Tax rule geolocation based.

I explain me better (sorry, I am not pricese enougth):
- I must have taxe depending on geolocation because, in Guadeloupe the VAT value is different than in France. So I have to know where my user comes from.
- I cannot fill the VAT number field because in Guadeloupe, the company don't have VAT number, even if there is VAT.
So regarding to all that parameters, I am a little bit lost about what to do.

VAT is only used for Business tax. You can do geolocation taxes without VAT. VAT only works if Company is supplied.

- If I said my user "When you are in the basket, modify your information form to add the country, then when they will see the value of the basket inscrease because of the tax, many of them won't want to be honest an correct the form.

Of course they can, that's how every site works where you supply location data before purchase. You don't explicitly tell them to complete it. You just set invoice address to mandatory then they don't have a choice. You then calculate tax based off this selection. Someone changing it to a country that charges less tax is no different then changing to a VAT with lower tax.

You could even use PayPal then in PayPal setup taxes to be forced based off billing address and they can't fake the credit card billing address as it's validated by PayPal against the cards bank.

Will we be inform when the new release will be ready with the problem solved please ?
Now I set "to put the same VAT for averybody in the world" but I can't stay like this so long.

VAT is already working fine. The jQuery just isn't firing when clicking to edit invoice address and the fields are pre-populated. We do not have a timeframe for a new release, sorry.

I strongly suggest reading the CBSubs documentation. It explains CBSubs tax usage and details its various parameters. There is nothing you can do to force users to be honest.