Hi @Mtdennin 

Do you know which version of Nintex forms you are using?

For the older forms designers it would be done by adding in a rule on the control you would like to validate, you would then build a formula to match the criteria you need, for example. contains(‘x’)

For the newer forms designers there is a section in the rules designer for form validation that is much better and can apply much more complex logic.

Let me know which version you have and I will try provide more detailed steps.

Jake

Hi @Mtdennin,

I think it would be easier to to write a rule around the format you want and not the format you don’t want.

In a control’s configuration you can set the validation to regular expression and then write a regular expression to match the format you want.  Anything outside of that would error.
Example: