No that isn't possible, you will need to use the template provided to upload your data. The reason we need to use a specified template is so that our program can correctly map the right input data to the correct output required by Tally.
When you click the upload file button, the system first checks to make sure that the file is of the correct format and has not been tampered with. Then a check is done to ensure that the Ledgers in the entries are matching with the Ledger list as per Tally - this step makes sure that the Tally Import process doesn't fail due to a missing Ledger or spelling mistake. The system will notify you in case of any issues to correct.
If there are no issues, the system will convert the input Excel data into the XML format required by Tally and provide you a link for download. Once you download the XML file, click on the link provided on the same page to delete your session data and the uploaded / processed files.