>>Let B = base amount = $500
>> T = tax amount = $74.88
>> F = Federal tax % = 5
>> P = Provincial tax % = 9.5
>>
>>
>>if we know T, F and P then B can be derived as follows:
>>
>> B = (T*100) / ( F + P + (F*P)/100)
>>
>>Having derived B you can the calculate the Federal tax amount as B * (F/100)
>>and the Provincial Tax amount as B * (1+(F/100)) * (P/100)
>
>Thanks
>
>This is close but does not give the exact amount:
>
>(74.88*100) / ( 5 + 9.5 + (5*9.5)/100)
>
>...gives 500.03$
>
>I tried something like that last night but was never able to obtain the exact number.

The way to do that is towards the end of Re: Decimal precision Thread #1544101 Message #1544116