Hi there, @Tennis11. 

Changing the sales price or rate won't affect your past invoices in QuickBooks Online (QBO). It will only affect your future invoices when you create them. To learn more about it, check out this article: Change product and service item types in QuickBooks Online.

For future reference, you may visit this article to learn how to personalize and add specific info to your sales forms: Customize invoices, estimates, and sales receipts in QuickBooks Online.

If you have any follow-up questions about the item sales price or other QuickBooks-related concerns, simply leave a comment below. I'd be glad to answer them for you.