In this article I will explain with an example, how to implement GST Number validation using Regular Expression (Regex) in jQuery.
 
 
HTML Markup
The following HTML Markup consists of an HTML TextBox, SPAN and a Button.
GST Number:
<input type="text" id="txtGSTNumber" />
<span id="lblError" class="error">Invalid GST Number.</span>
<hr />
<input type="button" id="btnSubmit" value="Submit" />
 
 
Validating GST Number using Regular Expression in jQuery
Inside the jQuery document ready event handler, the Submit Button has been assigned a jQuery Click event handler.
When the Submit Button is clicked, the GST Number TextBox is referenced and its value is tested using a Regular Expression.
The following conditions must satisfy for a GST Number to be termed as valid.
1. It should be 15 characters long.
2. The first 2 characters should be a digit representing State Code.
3. The next 10 characters should be PAN number of the taxpayer.
Note: For more details on PAN Card Number validation, please refer my article PAN Card Number validation using jQuery and Regular Expression.
 
4. The 13th character should be any digit (1-9) or an alphabet.
5. The 14th character should be Z by default.
6. The 15th character should be an alphabet or any digit. 0-9.
Example: 06BZAHM6385P6Z2
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
    $(function () {
        $("#btnSubmit").click(function () {
            var regex = /^[0-9]{2}[A-Z]{5}[0-9]{4}[A-Z]{1}[1-9A-Z]{1}Z[0-9A-Z]{1}$/;
            if (regex.test($("#txtGSTNumber").val())) {
                $("#lblError").css("visibility", "hidden");
            } else {
                $("#lblError").css("visibility", "visible");
            }
        });
    });
</script>
 
 
CSS Class
The following CSS classes are used.
1. error – It will apply RED color to the error message.
2. gst – It will force the letters to be UPPER case.
<style type="text/css">
    body { font-family: Arial; font-size: 10pt; }
    .error { color: Red; visibility: hidden; }
    .gst { text-transform: uppercase; }
</style>
 
 
Screenshot
GST (Goods and Services Tax) Number validation using jQuery and Regular Expression
 
 
Browser Compatibility

The above code has been tested in the following browsers.

Internet Explorer  FireFox  Chrome  Safari  Opera 

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Demo
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Downloads
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