Can I increase the calculated federal withholding tax?

Allow me to enlighten you about modifying your federal withholding tax, idf_5c.

Taxes are calculated automatically in QuickBooks Online (QBO) Payroll. We can't edit the federal withholding tax amount. 

The Federal Income Tax (or withholding) is based on the following factors below:

1. Employees' W-4
2. Pay frequency
3. Gross wages
4. Percentage/wage bracket method

Thus, a workaround is adding an extra withholding to increase the calculated amount. Please refer to the steps below:

1. Go to Payroll and choose Employees.
2. Select the employee. Then, scroll down to the Tax withholding section and click Edit.
3. Tap the Federal withholding dropdown and make the modifications in the Extra withholding box under Other adjustments section. 
4. Hit Save.
   
   
   

Furthermore, check out this resource to help you view information about your business and employees: Run payroll reports.

I'll be around if you have other concerns about managing your federal withholding tax or running payroll reports in QBO. Take care!