The Sales Items part are used to set the taxes, payment types and sales items.
Taxes like the VAT and possible other taxes like City tax, are not changed often but very often used. The correct set up of the taxes is therefor critical.
Payment types are not changed often either, they require a one time set up in most cases.
Sales items can and will vary often and will need a more constant management. Sales items are all items sold in the hotel, from the Room to the candy in the lobby. Also all Food & Beverage should be added here as they can’t be added to the invoice.