You'll need to enable to tip-tracking feature in QuickBooks Online (QBO) before you can proceed, @Barnslade. I'll share with you the steps.

Here's how:

1. Go to the Gear icon.
2. Select Account and settings.
3. Click the Sales tab.
4. Tap the Sales form content section, then enable the Tips (Gratuity) feature.
5. Hit Save, then Done.

You can then add tips to your employee's checks. Follow the steps below:

1. Click the + New menu.
2. Select Check.
3. Pick the employee under the Choose a payee drop-down menu.
4. From the Bank Account drop-down menu, choose the account from where you're making the liability payment. 
5. Under the Category column, enter Undistributed Tips, then type in the amount under the Amount column. 
6. Fill up the other fields as necessary, then hit Save and Close.

See this article for additional information about this process: Share tips with your team. 

I'll share this article with you as well: Cash tips vs paycheck tips. It has a short description for each type of tip, and when to use them. 

Don't hesitate to drop a comment below if you have other questions about tips in QBO. I'll get back to you as soon as I can.