Hello there @keafisher,
Let's add a line item for tips so we can include it in your invoices.
Before recording it to your invoice, you would need to choose an account to use for your tips.
Then, let’s create new service item and name it "Tips".
Once done, you can then locate Tips under the PRODUCT/SERVICE column of your invoice and add it from there.
You might also want to read this article if in case your employees are receiving tips: How to Record a Tip and Add Tips on the Employee Paycheck.
Please let me know if you need any other assistance. Have an awesome day!