"0" is not detected as a digit by the system

[Kal_Lam]

@anilgnydn, maybe if you have not gone through this post previously:

Leading Zeros Not Accepted in Regex constraint

Have you tried this: In the survey tab of your xlsform: [image] It should solve your issue (i.e. users are only allowed to enter 3 digits from 001 to 999). Reference xlsform: Regex_Constraint.xlsx (10.0 KB) If you are still facing an issue, please share with us a screenshot of the issue. The community would love to help you solve your issue. Note: if you wish to have the numbers between 000 to 999 you could simply change the regex code to (regex(., '^[001-999]{3}$') and (. >= 000))