Bonjour Jean-René,

>I am looking for a formula that can give me the amount of sale before tax.
>
>I have a amount and I know the rate of Canadians taxes ( GST and PST) and I >like to found out was the amount before taxes for the GST and PST.
>

In France, we've got only one taxe called TVA, the next formula must work for your calculation, all depending how your GST and PST are calculated (wich is the first taxe applied to your sale, GST or PST ?)

Ex. : Sale After Taxe = Sale Before Taxe + Sale Before Taxe x TaxeRate / 100
SAT = [1 + (TaxeRate/100)] x SBT
SBT = SAT / (1 + (TaxeRate/100))

You might do it two time, using (for the first time) the last taxe, and for the secong time the first taxe.

Hope this can help, sorry for the explanation, my english does not allow me to be more explicit.

Roman,
A+