payment.md in razorpay-3.1.0

- old
+ new
@@ -814,13 +814,56 @@
 ```
 
 **Response:** <br>
  please refer this [doc](https://razorpay.com/docs/payments/third-party-validation/s2s-integration/methods-api/#fetch-payment-methods) for response
 
-```
+
 -------------------------------------------------------------------------------------------------------
 
+### Token IIN API
 
+```rb
+tokenIin = "412345";
+
+Razorpay::Iin.fetch(tokenIin);
+```
+
+**Parameters:**
+
+| Name       | Type   | Description                       |
+|------------|--------|-----------------------------------|
+| tokenIin* | string | The token IIN. |
+
+**Response:**
+```json
+{
+  "iin": "412345",
+  "entity": "iin",
+  "network": "Visa",
+  "type": "credit",
+  "sub_type": "business",
+  "issuer_code": "HDFC",
+  "issuer_name": "HDFC Bank Ltd",
+  "international": false,
+  "is_tokenized": true,
+  "card_iin": "411111",
+  "emi":{
+     "available": true
+     },
+  "recurring": {
+     "available": true
+     },
+  "authentication_types": [
+   {
+       "type":"3ds"
+   },
+   {
+       "type":"otp"
+   }
+  ]
+}
+```
+-------------------------------------------------------------------------------------------------------
 **PN: * indicates mandatory fields**
 <br>
 <br>
 **For reference click [here](https://razorpay.com/docs/api/payments/)**
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