Warning - rant ahead...
There seems to be a new trend in fundraising by FLOSS Foundations of sending automatic "renewal invoices" for corporate memberships/sponsorships. I've gotten 3 in the last 3 weeks. Most corporations, at least in the US, including Google, use (aka require the use of) purchase orders. When you send an invoice without a pre-issued PO# on it, the invoice will be rejected. Full stop. Please - save everyone some time and DON'T SEND AN INVOICE BEFORE YOU GET A PO#.
And before you start to explain how much better your automatic invoice system is for your org: don't bother. The PO# requirement is not up to me, there is nothing I can do about it, I don't like it either and arguing with me won't change anything.
Thanks in advance!