If you have chosen Manual check in AP-B and end up choosing cancel (usually because we have picked the wrong checking account) it does not cancel the process.   You end up with check number 0 zero.
You can see check #0 when you view AP-Q but since it is a manual check you must reverse the voucher thru AP-B.  But when you reverse the voucher you can't enter check 0.   I enter a bogus number because I do not know what to do.    
 
I can work through this issue, but I think it is clumsy not to be able to cancel a manual check mid process. And even worse for it to use check #0.
 
I also realized that we have created checks with  zero ch numbers  this way and didn't know it.   So if you are missing checks they may be in there with a zero check number.  
Thanks  
Laura

I am going to start changing the zero "0" check numbers to the correct check number viz BKAPCHKH, rather than reverse  voucher thru AP-B.