You've done the right thing to post your concern about online banking here in the Community. I presume you're doing reconciliation (consolidate) and I will help you solve this. Reconciliation or merging of accounts?
The number one rule in reconciliation is to make sure your transactions in the bank register are the same as the transactions in your bank statement.
If you've already reconciled the previous months, check their reconciliation reports to find any reported changes. These changes would surely affect the beginning balance of your current reconciliation. You can refer to this article: Fix issues for accounts you've reconciled in the past in QuickBooks Online.
Let me know if you have questions about the references I gave you. I just want to make sure you're all set, so you can move on to other tasks.
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