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  1. I need to create a calculation for Excel or on paper to (not a website or app): Partial refunds and sales tax to apply without knowing the U.S. State’s Sales Tax Rate.

Example of problem: If I know my subtotal is: $\$27.99$ And my Tax Amount is: $\$1.96$ How can I know that the Tax RATE is: $7.00\%$ ?

Excel: How do I express this in a formula in Excel allowing for manual entry of field 1 (pre-tax amt), field 2 (tax amt paid) = Rate

  1. For Canadian refunds need for Excel formula: GST, PST (Federal Rate 8%, Provincial Rate 5%) are needed some times together, a calculation with IF statement (if GST, then 8%, IF PST 5%, IF GST AND PST then 13%).

Research: Website has a calculator tool that is an example:

  1. http://www.csgnetwork.com/salestaxpercentcalc.html
  2. http://www.calculconversion.com/sales-tax-calculator-gst-qst.html
M.G. Mitchell
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    $\dfrac{1.96}{27.99}\approx 0.0700$ – Henry Aug 28 '21 at 16:22
  • Thank you for fast reply, Henry! (You also helped me to rephrase my question a little better) I appreciate your answer. – M.G. Mitchell Aug 28 '21 at 17:26
  • In case it helps, an initial translation from verbal to math is: $1.96$ is what percent of $27.99$? Letting $r$ be the number of percentage points (i.e. if the percentage is 7.2%, then $r=7.2),$ we can rewrite this as: $1.96 = (r%)(27.99)$ (translating "is" as =, and translating "of" as multiplication). Dividing both sides by 27.99 (to isolate $r%)$ gives $\frac{1.96}{27.99} = r%,$ which becomes $0.070025\ldots = r%.$ Since $r%$ is interpreted as $\frac{r}{100},$ we get (after multiplying both sides by $100)$ $7.0025\ldots = r.$ – Dave L. Renfro Aug 28 '21 at 17:42
  • Thank you, Dave! – M.G. Mitchell Aug 29 '21 at 02:54

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