What is a booking code, and how long does it last?
A booking code is a short reference, like TYRX0E, that a bookmaker gives a list of selections so anyone can load the same slip. It only works on the bookmaker that issued it, and it stops being useful once its matches kick off.
Why a code only works on one bookmaker
The code points to a slip stored on that bookmaker's server. Another bookmaker can't read it, which is why converting means rebuilding the same selections on the other site and getting a new code there.
How long a code lasts
A match that has kicked off can't be added to a new slip, so each started match drops out when you convert. Once every match has started, the code can't be converted at all, and ConvertSlip says so rather than returning a broken code.
Codes and countries
The same bookmaker in two countries issues separate codes. Always pick the country the code came from.
Questions
Can one code have selections on the same match twice?
No bookmaker accepts two picks on one match in a slip. When merging codes, ConvertSlip keeps identical picks once and asks you to choose when they differ.
Is a booking code the same as a bet slip?
It's a saved slip without a stake. Loading it on the bookmaker fills the slip; you still choose the stake and place the bet yourself.