I mailedl the books... 5 to the same person... but forgot to mak them as mailed prior to the deadline.

Have I lost all the credits that I would have earned?

How many days after the deadline did you forget to mark mailed?  Hopefully there are no other copies of the books in the system.  If there are other copies available in the system the orders will roll over to another member.  That would not be good.  

Pm the receiver and tell them you forgot to mark mailed but you mailed on (date).  Ask them to mark the books received in their Transaction Archive when the books arrive.   

PM the receiving member (that info should be in your transaction archive), explain what happened, let them know the books were mailed on -- fill in the date -- and ask them to cancel any requests that rolled over to other members. If requests have rolled over and that request has been mailed, the member does not owe you a credit because you forgot to mark the book mailed. Any that are cancelled in time, and your book is the only one going to them, then all is well and they can and should mark it received in their transaction archive. But to answer your question, if another copy was requested for the member and not cancelled before the sender prints the mailing label, then you are out of luck and you will not receive credit for mailing.

It could also depend on the receiver.  I just received a book from someone who forgot to mark it mailed.  When I got it I told her, and had no problem seeing she got her credit.  Why would I want to screw someone who just gave me a book?  So what if it takes a few extra days.  I'm not keeping my credit for that.  It seems petty and unnecessary. 

JoAnne,  if the system ordered books from other senders it can cause a mess for the receiver.  Sometimes the receiver has no idea that the original order was not mark mailed by the deadline.  Then the system orders the books from other members if available.  The receiver is NOT notified of these events.  If you are not paying careful attention you will not know this has happened.  Then books arrive and then the same books arrive from someone else, a mess! 

Yes, that is exactly what can happen...the requestor ends up with 2 books going to them and it is easy to mark the one book received, giving credit to the person who started the whole mess by forgetting to mark it mailed, and then the 2nd person who the book was requested from does not receive a credit, yet they did nothing wrong! Forgetting to mark a book mailed causes all sorts of problems for everyone else...it is a very bad mistake to make! And anyone who downplays it hasn't been affected by another member's mistake...there is nothing petty about it.

What Sally said, in her first post.

For the same reason PBS guidelines recommend waiting 2 weeks to re-order a book that has been declared lost in the mail...so the requestor doesn't receive two copies (and not know how or if to mark them received).