I am under the impression that it is important to invoice for services. The French love a papertrail after all. I use Wave online invoices, but will next month use Zoho Invoices as Wave has pulled out of Europe. Both are free.
@Berniemac you’ll find this webpage has the answer you want.
Of all the websites out there, I find Portail Autoentrepreneur one of the most comprehensive. You might be hard pushed to tick all the boxes for correct facturation if you are doing it respectively. To be fair, my electronic invoices are not up to the standard required described in this article, and I don’t have an intercommune TVA number. There was too much paperwork to do when I got set up. I have already billed UK clients. So fingers crossed that I don’t get an audit.
The easiest thing to do is invoice them in Euros and let them deal with conversion.
Tim