If you are a successful songwriter it doesn’t just mean you write great songs. It also means that you take care of your business so you can be paid. When you co-write for a career (as Shelly Peiken has done her whole life), you have to be smart about making sure that you and your co-writers have each agreed on their share of the song.
Even in my workshops I witness co-writes in class and am always amazed at how very fearful people are of ‘saying the wrong thing’ or not 'offending the other person.' But this mentality means that you will end up sabotaging yourself.
Asking for clarity on song splits should be a routine discussion. You are only as powerful as your voice is.
For as long as I can remember, I have had a form that I made for my writers that made it very simple: Name of the song, writers and their info, splits, date and voila! You politely ask your co-writer to sign it before they leave the session and now you have proof of what transpired so 2 years later when the song is cut, memories don’t go south.
Talk about it.