JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/jquery.mask/0.9.0/jquery.mask.min.js"></script>
<script src="https://code.jquery.com/ui/1.11.1/jquery-ui.min.js"></script>
                    <fieldset id="Fiscal" class="Fiscal">
                        <legend><b>Fiscal:</b></legend>
                            <label for="Natureza">
                            Natureza:   
                            <select name="NATUREZA">
                                <option value="1">Pessoa Fisica</option>
                                <option value="2" selected>Pessoa Juridica</option>
                                <option value="3">Trading</option>
                            </select>
                            </label>
                            <label for="CGC">
                            CGC:<input type="text" class="CGC" name="CGC" id="CGC" value="" />
                            </label>
                            <label for="INSC_MUNIC">
                            Insc. Municipal:<input class="class5" type="text" name="INSC_MUNIC" MAXLENGTH="11" value=""/>
                            </label>
                            <label for="INSC_EST">
                            Insc. Estadual: <input class="INSC_EST" type="text" name="INSC_EST" value=""/>
                            </label>
                            <label for="ST">
                            ST:
                            <select>
                                <option value="1" selected>SIM</option>
                                <option value="2">NAO</option>
                            </select>
                            </label>


                    </fieldset>
                    </div>

JavaScript

$(function() {$( "#datepicker" ).datepicker();});  
$(function() {$( "#tabs" ).tabs();});
$(document).ready(function(){
    $("input.INSC_EST").mask("999.999.999-9999", {reverse: true});
    $("input.CGC").mask("99.999.999/9999-99", {reverse: true});
});