In writing that estimate, which program do you use?
I believe the sales tax is added prior to the 10% Overhead and 10% Profit. The contractor should get 10 & 10 on the sales tax, because he has to manage the payment of the sales tax.
I do not believe sales tax should be added to the O & P.
This is how the estimating program I have used for many years calculates it
However, I have never had the opportunity to adjust in Canada.
I Post Large, it is easy on old eyes!!