To convert XLS to OFX (Excel file to OFX format), you can use the following method.
IMPORTANT: this tutorial is not for Quicken import. Quicken does not import OFX files, only QFX (Web Connect) files. Use the Transactions app, CSV2QFX for Quicken imports.
Open your XLS file in Excel and examine it. If transaction columns do not have the header, simply add them (if possible)
Use the following sample CSV file (Excel opens it) as a guideline how your an Excel spreadsheet should look like for easy parsing
Select all transactions including the header (or just press CTRL+A) and copy to the clipboard (CTRL+C)
Download and install CSV2OFX, make sure the file is digitally signed by ProperSoft on PC and on Mac you should be prompted to allow running the app from an identified developer
Start CSV2OFX and click the Paste from clipboard button
Adjust the mapping if required
Examine the transactions on the Transactions tab for dates, amounts, memos, and other columns correctly assigned
Make sure to set account details as account number, bank id, currency is set to match the account settings in your accounting software. Some software like Sage, XERO do check them on the OFX file and if there is no match, refuse to import an OFX file.
Click the Save button on the Transactions tab to create the OFX file
The converter offers to save an OFX into the same directory as a CSV/Excel file. If you are using copy/paste method, you may need to change the directory to save the OFX file