Open Sales Order Report > Show Amount Remaining to Be Billed

This is currently logged as an Enhancement 26537. As an alternate solution, a Transaction Saved Search can be created.

1. Navigate to Reports > Saved Searches > All Saved Searches > New
2. Click Transaction
3. Search Title: Enter Title
4. Click Criteria
5. Click Standard
   • Select Type
     1. Type: Select any of
     2. Select Sales Order
     3. Click Set
   • Select Status 
     1. Status: Select none of
     2. Select Sales Order:Cancelled, Sales Order:Closed, Sales Order:Pending Approval
     3. Click Set
   • Select Amount Unbilled
     1. Amount Unbilled: Select greater than or equal to
     2. Value: Enter 1
     3. Click Set
   • Select Main Line 
     1. Main Line: Select Yes
     2. Click Set
6. Click Results
7. Click Columns
   Note: For every required field use the drop-down menu to select it and once adjusted click Add if needed. 
   • Select Document Number
   • Select Date
   • Select Name
   • Select Amount (Transaction Total)
   • Select Amount Unbilled
   • Select Formula (Numeric)
     1. Formula: Enter {‌amount}-{‌amountunbilled}
     2. Custom Label: Enter Amount Billed
   • Select Status
8. Show Totals: Enter Checkmark
9. Click Available Filters
   • Select Date
   • Show in Filter Region: Enter Checkmark
   • Click Add
10. Click Save & Run