# 2. Initialize IMP object

#### On the checkout page, initialize the IMP object using your [Merchant ID](https://portone.gitbook.io/docs-en/ready/3.).

{% tabs %}
{% tab title="JavaScript" %}
{% code title="Client-side" %}

```javascript
  var IMP = window.IMP;   // Can be omitted
  IMP.init("Merchant ID"); // Example: imp00000000 
```

{% endcode %}
{% endtab %}

{% tab title="JavaScript (ES Next)" %}
{% code title="Client-side" %}

```javascript
  const IMP = window.IMP; // Can be omitted
  IMP.init("{Merchant ID}"); // Example: imp00000000a
```

{% endcode %}
{% endtab %}
{% endtabs %}

{% hint style="warning" %}
Be sure to initialize the IMP object **only once**.
{% endhint %}

**Calling a sub-merchant (Tier) payment window**

{% hint style="info" %}
`IMP.agency('Merchant ID', 'ABC');  //`<mark style="color:red;">**ABC = Tier Code**</mark>
{% endhint %}