Gareth,

Both formulae are the same - you can check the business end of the
formula by taking off the IF part so you have SUM((a5)-(a5/a15)*c3)*c5.
The only thing that changes between the scenario 1 and 2 is the tariff
allowance changes from 200 to 400 minutes. With the IF test stripped
out, scenario one will answer with 1.00, change the tariff to 400 and
you will get -3.
It seems to me that what is driving the formula is the contents of
cells C16 and E16 - these are being used as comparators against the
answer of the SUM(...) formula - this is what will cause the answer to
change depending upon what is in these cells

Jon


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Jon Quixley
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