Getting the proper CSV format can be a challenge when using spreadsheet apps like Excel or Numbers. Here are some tips to getting a valid CSV format out of a spreadsheet app:
Make sure you always have a header row. That tells the import process what data is in each column. The column headers have meaning, so be precise.
When a cell is a text field that STARTS WITH A LEADING ZERO, make sure you explicitly mark the cell as text. The easiest way to do this is to type a single apostrophe then the number when adding data to the cell as in ‘01886 for the zip code 01886.
Always export with UTF-8 support enabled.
Export to a CSV format. Comma delimited not tab delimited and quoted strings if given the option.