The OTA is who we collect from, not who the invoice is for
An OTA that collected from the guest is the payer; the guest is still the person on the invoice; the commission is what the channel said, never a silent zero.
A channel booking has a shape the desk needs to see at a glance: who has the guest's money, what the hotel will receive, and who the invoice is made out to. Getting any of the three wrong makes the desk ask a guest for money twice or names a company on a bill that belongs to a person.
Who holds the money
The channel says, on every booking, whether it collected or the guest pays at the hotel. A prepaid booking moves to the OTA's account at check-in: the card shows the amount paid, balance from the guest 0, and the balance due from the OTA. Pay-at-hotel is a guest bill like any other.
Who the invoice names
The guest who slept in the room. The OTA is the payer on the bill, not its recipient — the owner's rule, after a desk found bills with no guest's name on them.
The commission
The channel states its commission, or it does not. When it does, it is posted as an allowance at check-out and the account already reads what is owed. When it does not, the field is not zero — it is unknown, and the settlement statement, when it arrives, fills it in booking by booking.
The tax
The channel says the tax too. A price stated with tax zero is a price with the tax inside it, and the night is posted at the base that gives the channel's total.