Please assist with date formula?

This works fine for Customer 1 [SM JOB]

var date BillingDate = [DW 1 BILLED];

var date SameDayNextMonth = (AdjustMonth($BillingDate,1));

If(Day($BillingDate) <= 15, Date(Year($SameDayNextMonth), Month($SameDayNextMonth),10),

                                           Date(Year($SameDayNextMonth), Month($SameDayNextMonth),25))

Now, I need a different date result for Customer 2

IF([NVR JOB]=true,

...the return date needs to be 30 days after the billing date.

Please advise...I cannot seem to get () in correct places.  thx