If you need to import data in Sumtracker, you need to save your file in CSV format
Normally, the file you export from Sumtracker is already in CSV format, and you can import it right away after making any changes.
Sometimes, excel automatically changes the format of the downloaded file to .xls.
There are 2 ways to fix this. You can use either of these
Using MS Excel
Go to File > Save As.
Save it as a Comma Separated Values CSV file from MS excel on your system.
Upload this file to Sumtracker.
Using Google Spreadsheets
Open this file in Google Spreadsheet on Google Drive.
Do File > Download > Comma Separated Values (.csv) file.
Upload this file to Sumtracker.
The first option is faster and works well. But if you are facing issues with that, the second option always works out.