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# Data handling tips

## Phone numbers in CSVs

Cells and columns in CSV don't have well-defined types so programs reading those CSVs generally infer the type from the values.

This can be a problem when opening a file with phone numbers which often start with a zero, and look like a number to programs reading CSVs.

When reading a CSV file, see if you can specify that such columns should be read as Text rather than letting the program infer the type.

![Example reading a CSV with the first phone number changed to text but the second will still be inferred from the data](/files/-Mi1ep-XnsUA-vlJPv1j)

After reading, if the columns were read as text, the zero-prefixes will remain. If the program read it as numbers, the zero prefix will have been lost.

To check that the file was saved correctly, you can open it in a text editor like Notepad to check that the zeros are still there:

![Small part of a CSV shown in a text editor with phone number cells highlighted, correctly maintaining their zero prefixes.](/files/-Mi1fSxM6fqnM9zulJqM)


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