Excel only allows number precision up to 15 digits. After the 15th digit
Excel changes those digits to 0 as you've experienced.

Enter the CC numbers as TEXT. Either preformat the cell as TEXT or precede
the entry with an apostrophe like this: '1234567890123456. The apostrophe
will not be displayed in the cell.

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Biff
Microsoft Excel MVP


"dreamer" wrote in message
...
I am entering credit card numbers in a column and I notice the very last
digit keeps changing to zero. I have the cell unlocked. Any suggestiong?