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HTML 

              
                <div class="accordion">
    <button class="accordion-btn"> <span>Cash Offers</span></button>
    <div class="panel">
        <button class="accordion-btn inner-accord"><span>Subscription</span></button>
        <div class="panel">
            <div class="content1"><input type="checkbox">Subscription</div>
        </div>
        <button class="accordion-btn inner-accord"><span>Auto Publish</span></button>
        <div class="panel">
            <div class="content1"><input type="checkbox">Cash Offers</div>
            <div class="content1"><input type="checkbox">Conditional Cash Offers</div>
            <div class="content1"><input type="checkbox">Cash Rebates</div>
            <div class="content1"><input type="checkbox">Conditional Cash Rebates</div>
            <div class="content1"><input type="checkbox">Formula Pricing Cash Offers</div>
        </div>
        
    </div>
    <!-- panel -->
</div>

<div class="accordion">
    <button class="accordion-btn"><span>APR Offers</span></button>
    <div class="panel">
        <div class="content"><input type="checkbox">Subscription</div>
        <button class="accordion-btn inner-accord"><span>Auto Publish</span></button>
        <div class="panel">
            <div class="content1"><input type="checkbox">APR Offers</div>
            <div class="content1"><input type="checkbox">Conditional APR Offers</div>
            <div class="content1"><input type="checkbox">APR Rebates</div>
            <div class="content1"><input type="checkbox">Conditional APR Rebates</div>
                    <div class="content1"><input type="checkbox">Formula Pricing APR Rebates</div>
        </div>
    </div>
    <!-- panel -->
</div>
<div class="accordion">
    <button class="accordion-btn"><span>LEASE Offers</span></button>
    <div class="panel">
        <div class="content"><input type="checkbox">Subscription</div>
        <button class="accordion-btn inner-accord"><span>Auto Publish</span></button>
        <div class="panel">
            <div class="content1"><input type="checkbox">Lease Offers</div>
            <div class="content1"><input type="checkbox">Lease Rebates</div>
        </div>
    </div>
    <!-- panel -->
</div>
!

CSS 

              
                .accordion .content{
    padding: .5em 1.5em .5em;
}
.content1{
    padding: .5em 5em .5em;
}

$dark-blue: #2C3E50;
$dark-blue-highlight: #3f5973;
$pink:  #e01f32;
$off-white: #ECF0F1;
$baby-blue: #3498DB;
$blue: #5b80a4;
$blue-highlight: #7b99b7;

$color-main       : $off-white;
$color-background : $off-white;
$color-headlines  : $dark-blue;

@import 'https://fonts.googleapis.com/css?family=Montserrat';

$font-main: 'Montserrat', Helvetica, sans-serif;

* {
    font-size: 16px;
    font-family: $font-main;
}

/* Accordion Styles */
.accordion {
    width: 60%;
    margin: 0 auto;
    border: 1px solid $off-white;
}

/* Button Styles */
.accordion-btn {
    background-color: $color-headlines;
    font-size: 1.5em;
    color: $color-main;
    cursor: pointer;    
    width: 100%;
    text-align: left;
    border: none;
    transition: 0.5s;    
}

.accordion-btn span{
    padding-left:.5em;
}

.accordion-btn:after {
    content: '+';
    font-size: 1em;
    color: $off-white;
    float: left;
    margin-left: 2px;
}

/* Active and Hover Button Styles */
.accordion-btn.active,
.accordion-btn:hover {
    background-color: $dark-blue-highlight;
}

.accordion-btn.active:after {
    content: "-";
}

/* Panel Styles */
.panel {
    background-color: $off-white;
    max-height: 0;
    overflow: hidden;
    transition: 0.5s ease-in-out;
    opacity: 0;
}

.panel p {
    font-size: 1.2em;
    padding: 0 2em;
}

/* Show Panel onclick */
.panel.show {
    display: block;
    opacity: 1;
    max-height: 500px;
}

/* Inner Accordion Style */
.inner-accord {
    background-color: $blue;
    font-size: 1.2em;
    margin-left: 1.25em;
}

.inner-accord.active,
.inner-accord:hover {
    background-color: $blue-highlight;
}
!

JS 

              
                // Toggle 'active' and 'show' states of panels

var accord = document.getElementsByClassName("accordion-btn");
var i;

for (i = 0; i < accord.length; i++) {
    accord[i].onclick = function() {
        this.classList.toggle("active");
        this.nextElementSibling.classList.toggle("show");
    }
}
!
999px

Console