Once you mark an 'en route' book as received there is no way to undo this action. (The software simply doesn't "go backward" in that way.) Luckily, this usually is not a big deal - the book arrives soon after, and all it means is that the sender got credit early. 

• When you did this, the sender got credit for sending the book.
• You can contact the sender to discuss this if you want.  To do this:
  • Go to your Transaction Archive page under My Account in the toolbar at the top of the site
  • Scroll down to see the completed transaction for this book on the Transaction Archive page
  • Click to send a message to the other member

If you marked a book received with a problem and there was not a problem with the book, you can change the swap status as described in Follow-up on Problem swaps.  Doing this will not "un-mark" the book received, but it will remove the "problem" mark from the completed transaction.

If you marked a book received accidentally from the En Route to Me tab in My Account:

• This book was marked mailed; chances are that it will arrive.
• Please wait for your book; most likely it will arrive and you will have already marked it as received, and won't have to do anything further.
• If the book does not arrive within 26 days after it was marked mailed, let us know and we'll help!

If you DID receive the book but marked it "received with a problem" accidentally (there was no problem with the book):

• You can undo the "problem" status and change the status of the request to Completed Successfully using the Follow-up on Problem Swaps option, as described in Follow-up on Problem swaps.
• This will not undo the book's "received" status, but it will no longer appear as a problem swap.

If you marked a book received accidentally from your Transaction Archive:

• You may have thought that the Transaction Archive is the place to mark active incoming books received, but it is not.
  • The Transaction Archive shows only past transactions (including those that were declined by the sender, and never mailed)
• OR you may have thought that you forgot to mark a book received in the past.
  • This is possible, but is not always the case.
• To ensure you are marking the correct book received from the Transaction Archive in future:
  • Sort the Archive by  Requested by Me - All - Title - Descending
  • Scroll down to find the title of the book
  • There may be multiple transactions for the same title (lost, canceled, successfully completed)
  • If there is a green checkmark on one of the transactions for this title, that means you marked one copy received already.
    • If you did not get a second copy of the book, you do not need to mark another copy received.
  • If there is no green checkmark on any of the transactions for this title, and yet you received a copy of this book:
    • Compare the sender's name and state of origin on the right side of the transaction with the information in the return-address area on your package to determine WHICH copy was received
  • If there is no transaction for this title at all on your Transaction Archive
    • Click My Account in the top of the site, and then click the En Route to Me tab to see if there is an ACTIVE transaction for the book
    • If there is, you can mark the book received from the ACTIVE transaction.
      • The Transaction Archive shows only past transactions.
• If you marked a book received accidentally from your Transaction Archive, let us know and we'll help!

If you mark a canceled (or lost) transaction received from your Transaction Archive, a credit will be deducted from your account.

• When you do this, you are telling the system that you got THAT COPY of the book FROM THAT SENDER, and need to pay a credit for it, since you did not pay a credit for that copy from that sender (canceled and lost transactions do not take credit from the requestor).
• For instance, take the example of a Canceled Transaction:
  • When you request a book, the credit is deducted.  If that transaction is canceled, either
     
    • (1) your request is passed to a new sender (this will happen if there is another available copy of the book when the transaction cancels), and the new sender gets your credit when the book is marked received, or
    • (2) your request is canceled (if there is not another copy of the book available at that time), and you get your credit back.
  • If the canceled transaction resulted in scenario #1, then you paid your credit for one copy of the book (from the new sender), and if you then go and mark the canceled transaction received too, you are telling the system that you got 2 copies of the book and want to give a credit for the other copy.
  • If the canceled transaction resulted in scenario #2, then you never paid a credit for this copy of the book, and if you then go and mark the canceled transaction received, you are telling the system that you did get that copy of the book from that sender, and want to give a credit for it.

Related links:

Why are there canceled/lost books in my Transaction Archive that I know were sent/received?
How to Use the Transaction Archive
How do I refund credit(s) to another member?