Hello, Thomas. Thank you for reaching out, and I hope you're doing well too! Some banks limit the history available for download, which might explain the gaps in your QuickBooks Online (QBO) transactions. I'm here to guide you through how bank connections function in QBO, as well as get the transactions entered for those missing months.
When reconnecting accounts in QBO, keep in mind that some banks allow downloads for only the last 90 days, while others may offer up to 24 months. This likely accounts for the gap between May and July in your transactions. QBO relies on the information provided by your financial institution. To help prevent this issue in the future, I recommend regularly checking your bank connections to ensure timely syncing.
Moreover, to maintain account balance, manually upload the missing transactions into QBO. If you've downloaded them, proceed with the upload. I'll assist you through the process.
- From Transactions, click Bank Transactions.
- Click the blue tile for the account where you want to upload the transactions. Select the Link Account dropdown and hit Upload from file.
- Tick Drag and drop or select files and choose the file you downloaded from your bank. Then, pick Continue.
- Select the account you want to upload the transactions into in the QuickBooks account dropdown and tap Continue.
- Follow the onscreen steps to match the columns on the file with the correct fields in QuickBooks. Then select Continue.
- Pick the transactions you like to import. Choose Continue, and Yes, then Done to confirm.

On the other hand, to ensure your accounting transactions are accurately recorded, QBO lets you easily categorize them. For further assistance, kindly refer in this resource: Categorize online bank transactions in QuickBooks Online.
Once you upload the missing transactions, your client's financial data will be exact and reliable. If you have any questions or concerns about managing your bank accounts within QBO, don't hesitate to reach out. I'm here to understand your goals and provide the support you need to succeed.