# 2. Initialize IMP object

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

{% 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 %}


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://portone.gitbook.io/docs-en/auth/guide/2..md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.