Return filled checkbox

I've been able to solve the problem, so I'll post it here if someone goes through it, just change the json to receive only values that were actually checked / checked. And so I always return only the checkboxes that are marked in the database with Boolean value 1

<script type='text/javascript'>
$(document).ready(function(){
        $("input[name='id']").blur(function(){
                var $nome = $("input[name='nome']");
                var $inativo = $("input:checkbox[name='inativo']:checked");

                $.getJSON('function_pes.php',{ 
                        id: $( this ).val() 
                },function( json ){
                        $nome.val( json.nome );
                        $inativo.prop('checked', !!+json.inativo );
                });
        });
});

           <form action="salvar_pessoa.php" method="post"><!-- Inicio Form -->
                <div class="col-lg-2"><!-- Inicio Input ID -->
                    <label for="ex1">ID:</label>
                    <input type="text" class="form-control" maxlength="13"  name="id">
    </div><!-- Fim Input ID -->

    <div class="col-lg-5"><!-- Inicio Input Nome -->
                    <label for="ex1">Nome:</label>
                    <input type="text" required class="form-control" maxlength="50"  name="nome">
    </div><!-- Fim Input Nome -->

    <div class="col-lg-10"><!-- Inicio checkbox Registro Inativo-->
                    <div class="checkbox" style="margin-top:30px;">
                        <label>
                            <input type="checkbox" name="inativo" value="true" style="outline:none;">Registro Inativo
                        </label>
                    </div>

To change the state of a checkbox, use $inativo.prop('checked', json.inativo); . The value of a checkbox does not relate to its state, it just indicates what will be passed to the server if it is checked.