Hello, @kathleenquinn.

Let me share some information about the voided check in QuickBooks Online.

Correcting the date of the voided check is not possible, what you can do is to delete the transaction and recreate to change the void date. 

You may refer to this article to learn when to void or delete a transaction, and how to handle a situation if you create a transaction accidentally. Void or delete transactions. 

Feel free to fill me in if you have any other questions. Keep safe.