One check had wrong tax calc - from 3 months ago. What NOW?

Thanks for joining us here in the Community, @TexasFurniture.

I've got some information to share oh how you can keep your records accurate in QuickBooks Desktop after creating a manual adjust on your 941 form.

You'll need to create a payroll liability adjustment for the date where the taxes isn't calculated properly based on the Schedule B form. This way, your tax calculations, and payroll liabilities will be corrected so you can prevent this error from happening again.
 

To do that:

1. Go to Employees menu at the top.
2. Tap on Payroll Taxes and Liabilities.
3. Hit on Adjust Payroll Liabilities.
4. Supply the information needed in the Date, Effective Date, and Adjustment is for fields.
5. Select the employee.
6. Complete the Taxes and Liabilities fields.
7. Choose the Accounts Affected and then OK.
8. Repeat this for other employees if you need to, and press on OK.

However, to ensure the best course of action for your business, I recommend consulting your accountant. This is to help verify if these changes should affect your liability account. 

To give you the complete details on creating a payroll liability adjustment and on how to resolve errors in the Form 941/Sch. B - Employer's Quarterly Federal Tax Return, please see these references attached:

• Troubleshooting amounts in Form 941/Sch. B - Employer's Quarterly Federal Tax Return
• Learn how to use a liability adjustment to correct employees’ year-to-date (YTD) or quarter-to-date ...

You can always count on me if you have any other questions or concerns. I'll make sure you're taken care of. Have a lovely day!