diff --git a/README.md b/README.md
index e51e2893..44535ae3 100644
--- a/README.md
+++ b/README.md
@@ -220,7 +220,7 @@ Iamport.pluginMobileWebSupporter(webview)
 
 - Custom WebViewClient 의 사용
 
-[샘플앱의 예시 MyWebViewClient.kt](./app/src/main/java/com/iamport/sampleapp/ui/MyWebViewClient.kt)
+[샘플앱의 예시 MyWebViewClient class](./app/src/main/java/com/iamport/sampleapp/MyWebViewClient.kt)
 
 ```kotlin
 /**
@@ -249,6 +249,35 @@ class MobileWebViewModeFragment : Fragment() {
     }
 }
 
+```  
+  
+
+- Custom WebChromeClient 의 사용
+
+[샘플앱의 예시 MyWebViewChromeClient class](./app/src/main/java/com/iamport/sampleapp/MyWebViewClient.kt)
+
+
+
+```kotlin
+/**
+ [IamportWebChromeClient] 상속하여 사용
+ */
+// CASE 1 : IamportWebChromeClient 상속
+open class MyWebViewChromeClient : IamportWebChromeClient() {
+    override fun onJsConfirm(view: WebView, url: String, message: String, result: JsResult): Boolean {
+        Log.i("MyWebViewChromeClient", "called this function")
+        return super.onJsConfirm(view, url, message, result)
+    }
+}
+
+class MobileWebViewModeFragment : Fragment() {
+    override fun setupWebView() {
+        // IamportWebChromeClient 사용
+        it.webChromeClient = MyWebViewChromeClient()
+        // ..
+    }
+}
+
 ```
 
 </details>
diff --git a/app/src/main/java/com/iamport/sampleapp/MyWebViewClient.kt b/app/src/main/java/com/iamport/sampleapp/MyWebViewClient.kt
index c5642f2b..110ab4b7 100644
--- a/app/src/main/java/com/iamport/sampleapp/MyWebViewClient.kt
+++ b/app/src/main/java/com/iamport/sampleapp/MyWebViewClient.kt
@@ -1,8 +1,10 @@
 package com.iamport.sampleapp
 
 import android.util.Log
+import android.webkit.JsResult
 import android.webkit.WebResourceRequest
 import android.webkit.WebView
+import com.iamport.sdk.domain.IamportWebChromeClient
 import com.iamport.sdk.domain.strategy.webview.IamPortMobileModeWebViewClient
 
 open class MyWebViewClient : IamPortMobileModeWebViewClient() {
@@ -14,4 +16,13 @@ open class MyWebViewClient : IamPortMobileModeWebViewClient() {
         return super.shouldOverrideUrlLoading(view, request)
     }
 
-}
\ No newline at end of file
+}
+
+open class MyWebViewChromeClient : IamportWebChromeClient() {
+
+    override fun onJsConfirm(view: WebView, url: String, message: String, result: JsResult): Boolean {
+        Log.i("MyWebViewChromeClient", "called this function")
+        return super.onJsConfirm(view, url, message, result)
+    }
+}
+
diff --git a/app/src/main/java/com/iamport/sampleapp/ui/MobileWebViewModeFragment.kt b/app/src/main/java/com/iamport/sampleapp/ui/MobileWebViewModeFragment.kt
index 93a85bf6..bd482ffe 100644
--- a/app/src/main/java/com/iamport/sampleapp/ui/MobileWebViewModeFragment.kt
+++ b/app/src/main/java/com/iamport/sampleapp/ui/MobileWebViewModeFragment.kt
@@ -6,6 +6,7 @@ import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.Fragment
+import com.iamport.sampleapp.MyWebViewChromeClient
 import com.iamport.sampleapp.MyWebViewClient
 import com.iamport.sampleapp.databinding.WebViewModeFragmentBinding
 import com.iamport.sdk.domain.core.Iamport
@@ -43,6 +44,7 @@ class MobileWebViewModeFragment : Fragment() {
 
             // 통상적인 경우의 custom webviewClient
             it.webViewClient = MyWebViewClient()
+            it.webChromeClient = MyWebViewChromeClient()
 
             // oreo 미만에서 url 변경만 보고 싶은경우
             Iamport.mobileWebModeShouldOverrideUrlLoading()?.observe(this, EventObserver { uri ->
diff --git a/sdk/src/main/java/com/iamport/sdk/data/chai/request/PrepareRequest.kt b/sdk/src/main/java/com/iamport/sdk/data/chai/request/PrepareRequest.kt
index ec11973e..5d95aaa2 100644
--- a/sdk/src/main/java/com/iamport/sdk/data/chai/request/PrepareRequest.kt
+++ b/sdk/src/main/java/com/iamport/sdk/data/chai/request/PrepareRequest.kt
@@ -18,7 +18,7 @@ data class PrepareRequest(
     val pay_method: PayMethod = PayMethod.trans,//fixed
     val escrow: Boolean?, // true or false
     val amount: String, // 결제금액
-    val tax_free: String?, // 결제금액 중 면세공급가액,
+    val tax_free: Float?, // 결제금액 중 면세공급가액,
     val name: String, //주문명,
     val merchant_uid: String, // 가맹점 주문번호,
     val customer_uid: String?, // 정기결제용
@@ -47,7 +47,7 @@ data class PrepareRequest(
                 PrepareRequest(
                     escrow = false,
                     amount = amount,
-                    tax_free = Util.getOrZeroString(tax_free),
+                    tax_free = tax_free,
                     name = Util.getOrEmpty(name),
                     merchant_uid = merchant_uid,
                     customer_uid = customer_uid,
diff --git a/sdk/src/main/java/com/iamport/sdk/data/sdk/IamPortRequest.kt b/sdk/src/main/java/com/iamport/sdk/data/sdk/IamPortRequest.kt
index b548198e..e5aebfeb 100644
--- a/sdk/src/main/java/com/iamport/sdk/data/sdk/IamPortRequest.kt
+++ b/sdk/src/main/java/com/iamport/sdk/data/sdk/IamPortRequest.kt
@@ -16,14 +16,14 @@ import kotlinx.serialization.Serializable
 @Serializable
 data class IamPortRequest(
     val pg: String,
-    val pay_method: PayMethod = PayMethod.card, // 명세상 필수인지 불명확함, default card
+    val pay_method: PayMethod = PayMethod.card, // default card
     val escrow: Boolean? = null, // default false
     val merchant_uid: String, // default "random"
     val customer_uid: String? = null, // 정기결제용
     val name: String? = null,
     val amount: String,
-    val custom_data: String? = null, // 명세상 불명확
-    val tax_free: String? = null,
+    val custom_data: String? = null,
+    val tax_free: Float? = null,
     val currency: Currency? = null, // default KRW, 페이팔은 USD 이어야 함
     val language: String? = null, // default "ko", en, zh, jp => TODO validator 에 추가
     val buyer_name: String? = null,
@@ -36,7 +36,7 @@ data class IamPortRequest(
     val digital: Boolean? = null, // default false
     val vbank_due: String? = null, // YYYYMMDDhhmm
     private var m_redirect_url: String? = Platform.native.redirectUrl, // 콜백
-    val app_scheme: String? = null, // 명세상 nullable 이나, RN 에서 필수
+    val app_scheme: String? = null,
     val biz_num: String? = null,
     val popup: Boolean? = null,
     private val niceMobileV2 : Boolean = true,
@@ -96,7 +96,7 @@ data class IamPortRequest(
             var name: String? = null
 
             var custom_data: String? = null // 명세상 불명확
-            var tax_free: String? = null
+            var tax_free: Float? = null
             var currency: Currency? = null // default KRW, 페이팔은 USD 이어야 함
             var language: String? = null // default "ko"
             var buyer_name: String? = null
@@ -158,7 +158,7 @@ data class IamPortRequest(
                 this.custom_data = custom_data
             }
 
-            fun tax_free(tax_free: String) = apply {
+            fun tax_free(tax_free: Float) = apply {
                 this.tax_free = tax_free
             }
 
diff --git a/sdk/src/main/java/com/iamport/sdk/domain/IamportWebChromeClient.kt b/sdk/src/main/java/com/iamport/sdk/domain/IamportWebChromeClient.kt
index e160ff2b..cec790ad 100644
--- a/sdk/src/main/java/com/iamport/sdk/domain/IamportWebChromeClient.kt
+++ b/sdk/src/main/java/com/iamport/sdk/domain/IamportWebChromeClient.kt
@@ -7,7 +7,7 @@ import android.webkit.WebChromeClient
 import android.webkit.WebView
 
 
-class IamportWebChromeClient : WebChromeClient() {
+open class IamportWebChromeClient : WebChromeClient() {
     override fun onJsConfirm(
         view: WebView,
         url: String,
diff --git a/sdk/src/main/java/com/iamport/sdk/presentation/activity/IamPortMobileWebMode.kt b/sdk/src/main/java/com/iamport/sdk/presentation/activity/IamPortMobileWebMode.kt
index 44a71907..ac4eac26 100644
--- a/sdk/src/main/java/com/iamport/sdk/presentation/activity/IamPortMobileWebMode.kt
+++ b/sdk/src/main/java/com/iamport/sdk/presentation/activity/IamPortMobileWebMode.kt
@@ -64,7 +64,18 @@ open class IamPortMobileWebMode() : IamPortWebViewMode() {
             setLayerType(View.LAYER_TYPE_HARDWARE, null)
             clearCache(true) // FIXME: 안지워도 될까? 고민..
             visibility = View.VISIBLE
-            webChromeClient = IamportWebChromeClient()
+//            webChromeClient = IamportWebChromeClient()
+
+            webChromeClient = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+                webChromeClient.let {
+                    if (it is IamportWebChromeClient) {
+                        return@let it
+                    }
+                    IamportWebChromeClient()
+                }
+            } else {
+                IamportWebChromeClient()
+            }
 
             webViewClient = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                 webViewClient.let {