In order to constitute a proper invoice for payment, an invoice shall contain the following:
An agency may require a business concern to provide additional information which is helpful to the designated payment officer, but which is not essential. Failure of the business concern to provide this nonessential information with the invoice shall not render the invoice defective.
Invoices shall be considered received by the designated payment officer on the date a proper invoice is actually received in the designated office, or the date the agency accepts the property or service, whichever is later.
D.C. Mun. Regs. tit. 1, r. 1-1704