CBSubs 1.1 is implementing EU VAT numbers automated verification service.
EU VAT rules (linked from within the new CBSubs Taxes integration plugin for CBSubs) do not impose incrementing by 1 invoices.
CBSubs implements raising (timestamped) invoices numbers, which is enough for many countries.
Incrementing by 1 invoices issued is not an EU rule, but a national rule.
That said, we are implementing this feature as high priority, as a customer has now co-financed this feature, and it will be there in CBSubs 1.2 early next year.