I am trying to add a 15% service charge but it keep reverting back to .15

Welcome to the Community, @Michaellathan1.

Please know that there's no direct way to set up and enter a service charge in QBO. With this, I recommend sending feedback to our product developers team so this will be taken into consideration for future updates. Here's how:

1. Hit the Gear icon at the top, then select Feedback.
2. Type in your product suggestions.
3. Click Next to submit feedback.

In the meantime, you can manually calculate the charge of 15% to get the flat rate and create a service item or use the price rule feature. This feature lets you manage the price of your products and can offer discounts or charge different rates by item. To start with, make sure to turn it on from the settings. I'll guide you on how:

1. Go to Settings ⚙ and select Account and Settings.
2. From the Sales tab, go to the Products and services section, and click Edit ✎.
3. Toggle on the Turn on price rules Beta checkmark.
4. Hit Save then Done.

After enabling the feature, we can start creating a price rule. Here's how:
 

1. Go to Settings ⚙ and then select All Lists.
2. Choose Price Rules.
3. Click Create a rule. After your first rule, select New price rule.
4. Fill in the necessary details. 
   
   

Once ready to apply the customizations, just click the Apply rule. You'll see the adjusted prices of the item based on your customizations in the Adjusted price column. To save your rule, click Save and Close. 

You can visit this article that details the process: Set price rules in QuickBooks Online.

For future use, here's a guide to learn more on how to manage sales forms in QBO: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Keep in touch if you have other questions about adding a service charge or any other QuickBooks concerns. I'm always ready to assist. Take the best care!