Hi John,
There is no error.

You can't enter numbers with 20 significant digits.
See "Specification Limits" in HELP.

Calculation specifications
Feature Maximum limit
Number precision 15 digits
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HTH,
David McRitchie, Microsoft MVP - Excel [site changed Nov. 2001]
My Excel Pages: http://www.mvps.org/dmcritchie/excel/excel.htm
Search Page: http://www.mvps.org/dmcritchie/excel/search.htm

"john.bedford3" <john.bedford3@ntlworld.com> wrote ...
> I have been having problems with incorrect calculation of column totals when
> using the SUM function. The data I have entered in the column to 20 decimal
> places are as follows: 7.4, 10,14.7 and -32. These should total 0.1 but
> excel calculates the total as 0.09999999999999430000