3 different settings will need to be visited, to properly configure your Invoices module:  

1. Invoices settings (to establish your defaults)
2. Price Points settings (to establish markup amounts)
3. Work Orders settings (to enable auto-invoice generation)

     Go to Settings > Module Settings > Invoices > General

These are the default values used when creating new invoices.  
Billable Labor Rate: Set the default labor rate that should be used on customer invoices, unless otherwise specified on particular tasks.

     Go to Settings > Libraries > Price Points

Price Points are the most critical aspect of the Invoices. 
It sets the difference between your expenses, and what your customer is asked to pay. 

Each Price Point can establish the customers:

• Parts Markup Percentage (%)  
  • Displays the % increase over what was listed on the Work Order
• Labor / Service Hourly Rate ($)
  • Sets the Customer's Hourly Labor rate charged for each service performed on the work order
  • If nothing is entered, the invoice will default back to the Billable Labor Rate listed in the Invoice Settings Defaults
• Start Date / End Date
  •   Sets the length of the markup.  Price Point will not expire if the end date is left empty
• Apply this price point to all sites
  • If you have more than one Site/Entity, you can apply the price point to all, or choice which sites should be included
• Overrides
  
  • If Price Points are the rules, these are the exceptions
  • Establish an exception labor rate OR a fixed amount to be charged for a particular labor/service
  • Establish an exception part markup % OR a fixed amount to be charged for a particular part used

     Go to Settings > Module Settings > Work Orders > Work Type

Look at the list of Work Types, and decide which ones should be eligible to generate Invoices. 

• Select the desired Work Type
• Where it says Do you invoice for this Work Type?, switch the setting to    Yes   
• Lock in the change by clicking the    Save    button

Enabling this will create an invoice when the work order is completed​​​​​.

   NOTE:  Enabling this feature does NOT mean every work order under this work type will create an invoice.  

For it to generate an invoice, a completed work order must have two things:

1. Work Type that is set for Invoices
2. Have a Customer attached

If it doesn't have both, the work order will simply close without generating an invoice.

Now you can start closing work orders with work types authorized to generate invoices.

There will be exceptions that come up from time to time.  Simply return to the Price Points in settings, to add them in.
Any price point can be linked back to a customer.  Whenever you complete a customer work order, it will generate the invoice at their Price Point markup percentage. 

• Go to Customers 
• Select a customer record
• Select that customer record's Sites tab 

There, it will list each site the customer should appear on.  Select the Default Price Point from the list in the drop-down menu.
This is especially important if that customer's price point is different than the default for that Site/Entity