CO88 explanation

Hi Guys,

While running transaction CO88 we received error "reverse posting key specification is missing for posting key 91"

i've checked OB41 and noticed that the specification 81 for posting key 91 is missing.

now i know what to do but i have a doubt that may be you can clear.

we are doing the settle for Process order, now for some oroder it works CO88 for 4 of them not. where can see in the order the posting key?

if i input the missing specification what kind of impact i will have in my system?

thanks

C.