Thanks for taking the time to join this thread and share your concerns, @RLWD.

I'll elaborate more about reissuing lost checks in QuickBooks Online. 

To handle lost checks, I'd agree with the suggestion of Rainflurry above to make a bank deposit with today's date and assign it to the same expense, asset, or liability account as the original check. 

Otherwise, it would be best to seek guidance from your accountant if you want to use Journal Entry. The process can be tricky, requiring assistance to ensure the journals will be posted accurately to your accounts. Once you're ready, here's how you can create one: 

1. Click + New and select Journal entry.
2. On the first line, select an account from the Account field. It depends if you need to debit or credit the account. Enter the amount in the correct column.
3. On the following line, select the other account you're moving money to or from. It depends if you entered a debit or credit on the first line. Enter the same amount in the opposite column.
4. Review the amounts - you should have the same amount in the Credit column on one line and the Debit column on the other. It means the accounts are in balance.
5. Enter information in the memo to know why you made the journal entry.
6. Hit Save and new or Save and close.

For a more detailed step-by-step procedure for this process, check out this guide: Create journal entries in QuickBooks Online. 

Please let me know if you need clarification about managing your lost checks or if there's anything else I can do for you. I'll be standing by for your response. Have a great day, and stay safe.