A payment here is still open: either an unconfirmed gateway outcome (RequiresReview — the card MAY have been charged) or a gateway-accepted debit that hasn't settled yet (a Pending ACH with a TransactionId — money in flight). An unpaid Text2Pay link is NOT open; it holds nothing. Deliberately excluded from decimal InvoiceDto.AmountPaid so it never inflates a balance, but it still blocks void / revert / delete until the settlement sweep or a human resolves it.

"us-sales-tax" or "vat" — snapshot at estimate creation.

Set when this invoice was merged into a new combined invoice (it is then Superseded): the id of the successor bill.

Human-readable number of the successor combined invoice this one was merged into (set only on a Superseded source). Lets the UI link forward without a second fetch.

When the bill was issued (Draft → Unpaid) and its totals frozen. Null for Drafts and legacy invoices issued before the issue boundary.