In family law property matters, it's not uncommon for the parties to agree to split the fees for drafting and filing consent orders (particularly if the other party is unrepresented).
I made a costs agreement to that effect with the OP for limited scope works clearly stating they are not my client etc.
Do I have to create a new matter for this other party to be able to send them an invoice for half the fees?
Or is there a way to create two invoices within a matter, for each party to pay their half?