How do I adjust SUI contibutions for Qtrly Wages that exceeded $50K for quarter after checks were posted for a different rate?

I can guide you through how, @MickWein.

You'll have to update your SUI rate from the payroll settings. QuickBooks will automatically adjust your paychecks. Let me guide you how.

1. Go to Gear, then choose Payroll settings.
2. Next to the state you want to update, select the Edit ✎ icon.
3. In the State Unemployment Insurance (SUI) Setup section, tap Change or add new rate.
4. Enter your new rate and its effective date. For most states, the effective date is 1/1. For TN, VT, and NJ the date is 7/1.
   • If you have already created paychecks with the wrong rate, or need to correct a prior quarter rate, contact us.
5. If you have a surcharge or assessment tax rate, enter it here as well.
6. Enter your new rate and its effective date.
7. Click OK to save your changes.

For details, check out this guide: Update your State Unemployment Insurance (SUI) rate in QuickBooks Payroll.

Also, here's a link that'll help you manage payroll tasks. It has our general payroll topics with articles: View all help for QuickBooks Online Payroll. 

Feel free to let me know if you have follow-up questions or concerns with SUI rates. I'm always here for you. Take care and have a great day ahead.