From Confederate Treasury Certificates - A Collector's Guide to IDRs by George Tremmel, Pierre Fricke and Marty Davis.
The following definitions have been adopted to assist collectors in distinguishing the substitute forms and their usage, although in practice, regulations were less precise:
Certificate - a written representation that some formal act had been completed and executed. For example, an exchange certificate assures that a stated value of old currency had been delivered to a depositary and the holder is entitled to the stated amount of “new issue” currency.
Receipt - a written acknowledgment of a transfer of property to another. An example would be a depository receipt, which is written evidence that an official had accepted property from the person named. The more specialized Interim Depository Receipt (IDR) was evidence that a transaction for the property received was still pending.
Revenue certificates and receipts include documents that record bond purchases, currency issues, call certificates, refundings, exchanges, duties, tariffs, customs and taxes. These should always be distinguished from disbursement forms such as Treasury drafts, checks, requisitions, warrants, bills of exchange and departmental transfers.
Confederate IDRs and Exchange Certificates were issued in many different depositories in different towns across eleven Confederate States. This makes Confederate IDRs a rich area to collect, one that has generally gone under appreciated and one that presents ful and challenge. One can collect a favorite town, state or regions (e.g., Trans-Mississippi). Interesting collections may be built with as little a couple of thousand dollars.
Pierre Fricke, co-author, Confederate Treasury Receipts - A Collector's Guide to IDRs