Four consultants stay three nights. Their employer pays room and tax on account. Everything else — the bar, the laundry, the room service at eleven at night — is personal and settles individually at checkout.
Without sub-accounts this becomes a manual exercise on a Friday morning with four people waiting. Somebody prints the folio, highlights lines with a pen, works out the tax split by hand, and issues two documents that do not quite reconcile. It takes twenty minutes per guest and produces an invoice the company's accounts department will query.
With them, it is set up once at check-in: room and tax route to the company's window, everything else falls to the guest's. The routing rule is evaluated when each charge posts, so the bar round at 23:40 on the second night lands on the right side without anyone thinking about it.
Each window settles independently and gets its own invoice — the company's made out to the company, the guest's to the guest — rather than one document restating the whole bill.
Why this matters to you: corporate and agency business is the steadiest revenue an independent property has, and the reason it is painful is almost always billing rather than rate. A property that can split a bill the way the payer actually asked for it wins the second booking, and the twentieth.