Hi there,
Having the ability to add a percentage charge to your items on invoices means that you'll have more control of your bookkeeping. I'd be happy to help you set this up for specific customers.
If you're using a 10+ user license, you'll have the Advanced Pricing feature available to you. If you're using a license with less than 10 users, you can purchase the feature as an add-on. This is the feature you'll have to use to set up a new Price Rule.
Here's a really helpful article that explains how to turn on or purchase Advanced Pricing, as well as how to create a Price Rule: Use Advanced Pricing.
With Advanced Pricing, QuickBooks automatically changes the prices of items on sales forms according to rules you create. Each price rule can contain multiple conditions that must be met before QuickBooks Desktop changes the sales price. For example, if you want a specific group of customers (the first condition) to receive a discount, but only when they buy specific items (the second condition), set up a price rule with these two conditions. Conditions can be created based on customer, item, sales rep, date range, and class.
I hope this helps. Let me know if you have any other questions.
Have a great day!