You'll have to set up both items in the employee's profile so our program will calculate it, Mgmccpa12.

Although, 401k will also calculate on the wage since it's a deduction item.

I'll show you on how you can add them in the employee's profile:

1. Click Employees, then go to Employee Center.
2. Double-click the employee name to open their profile, then go to the Payroll Info tab.
3. Under Additions, Deductions, and Company Contributions, add the tips and 401k. 
4. Click OK. 

When you create the paycheck, these items will show.

If there's any other payroll questions, please don't hesitate to leave a comment below. 

@Kristine Mae 

The OP wants to know how to get a 401k, calculated as a percentage, to include Tips in the calculation.  You did not address the actual question with your answer.

@mgmccpa12 

To do this, make sure to list the Tip addition item before the 401k item, like this:

You can see here that the 10% 401-k deduction is calculating on $2000, including the Tips.

If you set up the employee record in this way, then it will be the default on new paychecks:

Hello,

I cannot get QB online to calculate Simple IRA pull from my tipped waitress!! Spent 3 hours on the phone with QB and they didn't help at all.

Any help would be greatly appreciated.

Hi there, KateM7.

Welcome back to the QuickBooks Community. We aim to deliver customer satisfaction at all times. And, this isn't the kind of customer service I desire you to experience. With this, may I ask if you encountered a specific error message? What happened when creating a paycheck? I appreciate any further details so I can present accurate details about calculating Simple IRA in QuickBooks Online.

Please know that you're always welcome to comment below and add additional information or if you have other concerns or follow-up inquiries about managing your contributions in QBO. I'm just around to help. Take care always.

Hello, 
thank you for reaching out.

QBO will not let me run my waitresses payroll when I set them up with their Simple IRA plan.

I receive this message "Net pay must be greater than 0. To pay Holly Boucher, increase the pay or decrease the deductions. To exclude Holly from this payroll run, clear the checkbox."

Not to sure what to do?

Good afternoon, @KateM7. 

I'm glad you came back to the Community to further your question about your waitresses payroll. Allow me to give you some information to help you out. 

The best way to resolve this message, is by doing the steps/actions the error is instructing. This will ensure that everything will be correct in your QuickBooks Online (QBO) account. 

Afterward, if you're still having a problem, don't hesitate to ask. I'm always here to lend a helping hand. Wishing you and your business continued success!

Ummm that's not much of an answer?

I found out by googling it. There are several steps to create a paycheck for a tipped individual who is contributing to their retirement.