This article covers 

Do promotional credits apply to one-time charges?

When do promotional credits apply to metered based billing?

Summary

Promotional Credits can be applied to all the upcoming invoices, both “recurring” and “one-time” charges.

However, there are two reasons when promotional credits do not apply to an invoice,

1. When you have configured usage-based billing (or) metered billing for your customers
   In this case, the credits get applied only when the invoice gets closed.
   
   

2. When the customer charged currency differs from the currency of the promotional credits
   For example, If an upcoming invoice that is in due for a customer is in HK dollars and the promotional credits are in USD.

Follow these steps to deploy the promotional credits:

• Change the currency of the promotional credits to match the invoice currency

• Void the existing invoice and create an invoice with the same currency as that of the promotional credits 

• Record payment (offline) against the existing due invoice and deduct the same from the promotional credits
  
  

Related articles and Documentation

What is the difference between deleting and voiding an invoice?

How can I add or deduct promotional credits for customers?