> **Source:** https://knowledge.leegality.com/document-execution/workflows/v4/setup-configuration/field-configuration
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# Control Input Format 

A **validation** controls the **format** of what is entered into a field in a v4 workflow — using character limits and a **Regex** (regular expression) pattern. For example, you can enforce a PAN pattern on the Internal Reference Number so that only correctly formatted values are accepted.

## What you can set

For each field, you can set a:

- **Minimum character limit**
- **Maximum character limit**
- **Regex** — a pattern the entered value must match.

## Add a validation

1. Right-click any field to open the pop-up.
2. Go to the **Validations** tab.
3. Enter the **Minimum character limit**, **Maximum character limit**, and **Regex** as needed.
4. Click **Apply**.

> **Info — Note**
>
> A validation applies to every field of that type across the workflow. For example, if you set a validation on the **Document Name** field, it applies to all Document Name fields in the workflow.

**What's the difference between a validation and making a field Mandatory?**

> **Mandatory** (a [Field Property](https://knowledge.leegality.com/document-execution/workflows/v4/setup-configuration/field-properties)) controls *whether* a field must be filled before proceeding. A **validation** controls the *format* of what is entered — and only runs if a value has been entered. For example, a **Minimum character limit** of more than 0 does **not** force the field to be filled; if the field is left blank, the validation is skipped and no error is raised.
> 
> A field can use both: **Mandatory** so it can't be skipped, and a **validation** so the value, once entered, matches the required format. Don't use a minimum character limit as a substitute for Mandatory — it won't have the intended effect on empty fields.