Bib transfer policy
Transfer of entries continues to be a controversial topic. The Houston Marathon, in Houston TX, no longer allows transfers.
The Steamboat Marathon, in Steamboat Springs CO, does, and gives specific instructions about how to do it.
Many races disqualify runners FOREVER if they compete with somebody else's bib number.
A runner who uses someone else's bib is not covered by event insurance and, if fast enough, may earn an award that registration records will assign to the rightful owners of the number, not the person who actually ran the race.
An entry is not a ticket to an event. It's like admission to a school - it can't be given away or sold.
If you want to allow transfers, design a procedure that encourages runners to follow your rules and does not create undue hardship for your event.