How to override or add another formula to the field function

[mmurphy]

Hi, I have a column where the tax of products is being calculated and in the field I have the formula to calculate the tax since it is the same for every product that can be taxed. I have certain products that do not include tax, so how to do write out a formula, or override my current one so these products do not automatically calculate the tax. 

Thanks!

[kuovonne]

Sounds like you could use an IF() function. It is documented in the Formula Field reference.

If you want more specific advice, I recommend posting screenshots of sample data (including the column headings that show field types of all relevant fields) and your current formula.