Spreadsheets are mainly used for handling tabular data: values in cells, arranged in rows and columns.

However, a spreadsheet is often much more than a flat table. Spreadsheets can be provided with more detailed layout, for example the use of color in cells or the representation of the lines between the cells. The structure of a spreadsheet can also be important. For example, cells can rely on calculations made based on values in other cells. Therefore, with spreadsheets, careful attention must be paid to the characteristics that are important to preserve; which “significant characteristics” are in the file.
The Open Document Spreadsheet (.ods) format is an open, reasonably well supported and robust spreadsheet format that is recommended as a preferred format for the sustainable storage of spreadsheets with calculations and / or other further (structure) properties.

Can a spreadsheet be seen or reduced to a flat table of rows and columns (without preservation of formatting)? Then you can choose to make a CSV (Comma Separated Values) text file from the table. See the CSV file section for a further explanation of how to use this format. CSV files are only suitable for storing flat tables. A CSV does not retain formatting (text or cells), formulas, links to external sources.

Is direct visualization the primary purpose of the spreadsheet? Then the file can possibly be treated as a formatted text file and offered as PDF/A. See the Text documents section for more information.
PDF/A is primarily suitable for the presentation of formatted tables. The format offers limited support for spreadsheet properties such as formulas and links to external sources.

 Preferred formats

• ODS (.ods)
• CSV (.csv)

Non-preferred formats 

• Microsoft Excel (.xls)
• Office Open XML Workbook (.xlsx)
• PDF/A (.pdf)