I'll help you clear this transaction in QuickBooks Online, Will.
You can record a reverse entry to void a transaction in another period instead of removing it. The transaction is still on file, so you can easily restore it.
Before you void the invoice, you can print a transaction journal for reference. Then, create a reversing Journal entry.
Here's how:
Go to + New.
Click Journal Entry.
Enter the date in the journal to show the transaction as reversed.
Enter the accounts in reverse based on the printed transaction journal.
Hit Save.
I'd also suggest contacting your accountant before performing these steps. This will help us make sure your books are accurate.