I can't import older transactions from Nat West. I've downloaded a csv of the right date range.

We can perform some troubleshooting steps to isolate the issue with importing your old transactions in QuickBooks Self-Employed (QBSE), @MJT3.

If you've done reviewing the column headers and data, ensure the Date, Description, and Amount columns on the CSV match the columns and order in QuickBooks. The other column headers can be in any order. However, you still get the same concern. Cookies and caches may prevent you from uploading those transactions in your QBSE company file. I'd suggest performing the basic browser troubleshooting process to fix it.

You'll want to restart your browser. Then, try uploading your transactions in an incognito or private browser. 

You can use these keyboard shortcuts to launch a new private window:

Google Chrome: press Ctrl + Shift + N

Mozilla Firefox: press Ctrl + Shift + P

Safari: press Command + Shift +

If it works, you can return to your regular browser and clear your browser's cache. Then you may see if it fixes the problem and gets started on the tasks at hand. You can use another supported browser if the private window doesn't work.

For further guidance, please refer to this article: Add older transactions to QuickBooks Self-Employed.

Once you've imported the transactions flawlessly, you're ready to categorise them and put them in the correct account. See this article for more detailed steps: Categorise transactions in QuickBooks Self-Employed.

If the issue still occurs, I'd like to ask if you have received any specific error when uploading your transactions.

You're always welcome to post if you have any other concerns or additional information about importing your data. Wishing you and your business continued success!