I can provide the steps on how to change the email address of the contractor, MCSadmin.
You may need to update the information through the Expense page. And, I'm glad to show you how:
- Go to Expenses from the left menu, then choose Vendors.
- Locate the contractor from there and open the profile.
- Select Edit.

- Edit the new email address.

- Select Save and close.
- Once done, refresh QuickBooks for changes to take effect.
If you want contractors to add their own tax information, you can invite them to QuickBooks Online.
Feel free to post again if there's anything else you need or leave a comment below if you have follow-up questions. I'll be right here to help you.