How do you combine different subscriptions?

What do you mean with "combine"? You can use the same email address to manage multi QBO accounts.

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Thank you for posting in the Community, @cnlmasonry-gmail. I am here to share some information about the subscription to QuickBooks Online (QBO). 

Currently, there isn't a direct way to combine 2 QuickBooks Online (QBO) subscriptions. However, you can transfer your data manually by exporting and importing the data to the company you want to keep.  Then,  cancel the other account to avoid extra charges and pay one account only.

To export the data:

1. On your QuickBooks account, go to the Gear icon.
2. Select which data you'd like to export.
3. Click on the Export to Excel button.

To import data:

1. Log in to the new account, then click on the Gear icon at the upper right.
2. Under Tools, choose Import Data.
3. Select the type of data that you'd like to import.
4. Click Browse to select a file to be imported.
5. Click on the Next button until finished.

You may also want to use a third-party application so you can transfer all the information into your new account.

Let me know if you have more questions or other concerns with your QuickBooks Online account. I'll be glad to answer them. Have a great day!