By system default if you were to deliver two items on the same date of service that were both designated with a rental price option, upon completion of the order a single invoice would automatically create with both items on separate service lines. 

In certain cases, you may want to split the rental items delivered on two separate invoices.

For example if you delivered oxygen and a ventilator to a patient but did not want to hold the entire invoice from being submitted due to documentation requirements such as a CMN outstanding, you could create a rental rule for a specific payer indicating which HCPCS codes cannot be combined with other items on an invoice. 

In this case, when the system generates the invoice it will create two invoices with the individual item on each.