Backing Out Sales Tax from Gross Total - Auditor Question

[Joanie824]

does anyone know the formula to back out sales tax from a gross total - I am an auditor and I need to back out sales tax ie:
gross sales 50,859.18 - this total includes sales tax at 12.25% - i need the formula to back out the sales tax form the gross sales - ANy one know??

 

[mgb_phys]

Simply divide by (1+sales tax), or in percentages (100+sales tax%)/100

So 50,859.18 / ((100+12.25)/100) = 50,859.18 / 1.1225 = 45308.85
45308.85 * 0.1225 = 5.550.33
45308.85 + 5.550.33 = 50859.18