Fifteen digits
Excel stores numbers with 15 significant digits of precision. A longer number is rounded to 15 digits and the rest are
filled with zeros. Excel's display then shows it in scientific notation because it does not fit the column:
2.02609E+17.
| In the file | Shown | Stored and saved |
|---|---|---|
202609100000012345 | 2.02609E+17 | 202609100000012000 |
4000123456789010 | 4.00012E+15 | 4000123456789010 |
40001234567890123 | 4.00012E+16 | 40001234567890100 |
The values most often hit: order and invoice numbers, shipping codes (an SSCC has 18 digits), database IDs of 18 or 19 digits, and anything that looks like a card or account number.
Why widening the column does not help
Widening the column or choosing a number format with no decimals only changes the display. The digits after the fifteenth were rounded away when the file was read; they are not in the cell to be shown.
How to keep every digit
In Excel, import the file (Data ▸ From Text/CSV) and set identifier columns to Text before loading. Or
open the file with an editor that does not convert: in Intact CSV Editor 202609100000012345 is kept as
the eighteen characters it is, shown in full, and saved back unchanged.
Where a column genuinely holds numbers of very different sizes — 0.000000041 beside
41000000000 — the inspector's Column tab can draw it in scientific notation or as plain digits.
That is drawing only; the file keeps exactly what it had.
A note on JSON
JSON has the same trap in JavaScript, where numbers have about 15–17 significant digits. Intact CSV Editor's JSON editor keeps a twenty-digit identifier exactly as it was written rather than turning it into a float.
Try it on your own file
Intact CSV Editor is free for seven days, fourteen with an account — every feature, no card. Download the free trial.
