Okay, I misunderstood what you meant.

That said, I feel like you're asking for something that is fairly non-standard in the industry in general, though I could be wrong; I've never tried to do things that way myself.

If I were fastmail, those tax issues they mention would definitely take precedence over other issues in any event. Writing your own sales tax/VAT/whatever software strikes me as a special kind of hell given all the tax laws that have to be supported (and kept updated!) for every different jurisdiction out there.

For me, being able to pay three years in advance and only have to renew once every three years is fine, and they did offer a workaround for you, but to each their own I suppose.