Русско-англо-русский юридический словарь

"Any communications (about giving or issuing consents, approvals, notices, etc.) should be in writing and delivered against receipt; and delivered, sent to the address for the recepient's communications."

I wonder if it's meant to be "upon" receipt?

It means "in exchange for".

Yes: 'receipt' in the above case means the signed document acknowledging receipt (acknowledging the fact that the goods were received). (WordReference.com)