Can I make a journal entry to reverse a check I wrote last year so it won't change my last year's financials.

I’m glad to see you in the Community, Mr MA.

Yes, you can make a journal entry to reverse the check. Before creating one, I recommend contacting your accountant first to check the specific categories to use in the debit and credit.

Once you have them handy, follow these steps to record the transaction. I’m here to help ensure the process is a breeze for you.

Here’s how:

1. In QuickBooks Online (QBO), go to the New menu in the upper left and choose Journal entry under Other.
2. Type the transaction date in the Journal date field.
3. Head to the first line and pick the category from the Account drop-down. Depending on if you need to debit or credit the account, enter the amount in the correct column.
4. On the second line, choose the other account you're moving money to or from and enter the amount.
5. Review the amounts and make sure they’re the same (Debits and Credits columns).
6. Click Save and close.

For more details, you can read this article: Create a journal entry in QuickBooks Online.

Also, these resources will guide you on how to set up an account, organized your chart of accounts, and handle the debit and credit in your journal entry.

• Add an account to your chart of accounts 
• Create subaccounts in your chart of accounts 
• Debit vs credit

Keep in touch if you have additional questions about creating journal entries. I’ll jump right back in to answer them for you. Enjoy your day and stay safe.

Found this very helpful link: https://www.youtube.com/watch?v=2_vWmw38ylg