From a draft. On any check in the Things-to-check panel, click Ask owner. The client sees the question on their portal, answers in one tap, and the answer is filed against that draft so the query trail lives with the books.
Missing receipts. When a bank line has no document behind it, the client's portal shows it under missing receipts with a prompt to clear them. Whatever they upload lands straight against that transaction. Their Monday email carries the count as a gentle nudge.
Any document. The client can also add any document from their portal or forward it to their documents address; it arrives in your intake queue marked as coming from them.