but we're required by law to do it.
I would have a chat with whomever told you that. I know for a fact you don't have to supply a VAT,
or a IRS number when you purchase WHMCS and they are a company based in the UK: UK Registered Company #6265962. Vat No. GB 927 7746 76
There is also Reseller-Club Mods which is a company outside of the USA that I have done business with as well and again there was no need for IRS numbers or VAT.
ResellerClub Mods (gIF)
C\Las Margaritas 39
35100 San Agustin
Las Palmas de Gran Canaria
España - Spain
Both of these companies are people I have done business with and both of them as you can see are outside of the USA.
All that said I don't know if the rules you are talking about are specific to your region, or not, but that is the experiences I have had dealing with people outside of the USA.