This issue seems to go even further that the manual work to figure out sales tax for an amount billed.
If you use quote to bill clients on a recurring basis with sales tax, because of this flaw, the sales tax won’t stick for any future invoice, only the first one. In other words, the end user has to go through the stripe subscriptions and update them all manually to add sales tax on future invoices. It is pretty crazy that this was missed, and not addressed since first reported in November.
Many hubspot users may be using quote and the integration without knowing this is going, and hence failing to collect sales tax.
I would lable this idea a bug rather than a feature add.. and one that would probably take a couple of hours to fix.