In QuickBooks, linking a bank account generally allows the download of up to 90 days of past transactions from most banks, @katiecavanagh.
Additionally, there might be a problem with your bank connection when transactions are being downloaded to your QBSE, which could result in some missing entries. In the meantime, you can manually refresh your bank connection to check if the missing entries appear.
Here's how:
1. Go to the Gear icon.
2. Select Manage accounts.

3. Click Refresh all.
Once done, return to the Transactions menu to check if the missing transactions are now displayed. Alternatively, if the transactions are still not showing, you can manually import them using a CSV file.
Additionally, it's important to categorize your downloaded transactions once they are in, to maintain the accuracy of your financial records.
Feel free to share another post or reply below if you need assistance with managing your bank transactions in QuickBooks Self-Employed.