Can i import bank feed transactions for one day only, which were missed back in september?

Hi info608

You can either manually add the transactions or yes, download the bank statement from your online account, in an Excel/CSV format, delete from the spreadsheet any transaction that have already been added to QuickBooks and then use the file upload option within the banking section, please ensure that you select the correct chart of account/bank account you want the spreadsheet to be connected to.

https://quickbooks.intuit.com/learn-support/en-uk/banking/import-bank-transactions-using-excel-csv-files/01/239741#M43