Inscrivez-vous ou connectez-vous pour rejoindre votre communauté professionnelle.
We need to divide the value of gross receipt with the Gross percentage, that is 100%+ the percentage of tax.
Let say the sales tax in your state is 8% and you went to Walmart to buy groceries for example and spent $100.
The tax amount should be $100 * %8/100 = $8 and so on.
I hope you got the general idea.