diff --git a/dist/chargebee-java-2.6.8.jar b/dist/chargebee-java-2.6.8.jar
index 0c426e58..525b117b 100644
Binary files a/dist/chargebee-java-2.6.8.jar and b/dist/chargebee-java-2.6.8.jar differ
diff --git a/src/main/java/com/chargebee/AsyncRequestInterceptor.java b/src/main/java/com/chargebee/AsyncRequestInterceptor.java
new file mode 100644
index 00000000..c9820aef
--- /dev/null
+++ b/src/main/java/com/chargebee/AsyncRequestInterceptor.java
@@ -0,0 +1,8 @@
+package com.chargebee;
+
+import com.chargebee.internal.AsyncResult;
+
+public interface AsyncRequestInterceptor {
+
+    public AsyncResult handleRequest(AsyncRequestWrap requestWrap) throws Exception;
+}
diff --git a/src/main/java/com/chargebee/AsyncRequestWrap.java b/src/main/java/com/chargebee/AsyncRequestWrap.java
new file mode 100644
index 00000000..e4f68202
--- /dev/null
+++ b/src/main/java/com/chargebee/AsyncRequestWrap.java
@@ -0,0 +1,21 @@
+package com.chargebee;
+
+import com.chargebee.internal.HttpUtil;
+import com.chargebee.internal.ListRequest;
+import com.chargebee.internal.RequestBase;
+
+public class AsyncRequestWrap<T extends RequestBase> {
+    public final Environment env;
+    public final T request;
+    public final boolean isListRequest;
+    public final HttpUtil.Method method;
+    public final String uri;
+
+    public AsyncRequestWrap(Environment env, T request, HttpUtil.Method method, String uri) {
+        this.env = env;
+        this.request = request;
+        this.method = method;
+        this.isListRequest = request instanceof ListRequest;
+        this.uri = uri;
+    }
+}
diff --git a/src/main/java/com/chargebee/Environment.java b/src/main/java/com/chargebee/Environment.java
index c04a1822..9b2ed24e 100644
--- a/src/main/java/com/chargebee/Environment.java
+++ b/src/main/java/com/chargebee/Environment.java
@@ -39,6 +39,8 @@ public class Environment {
     private static Environment defaultEnv; // singleton
     
     private RequestInterceptor reqInterceptor;
+
+    private AsyncRequestInterceptor asyncReqInterceptor;
     
     public Environment(String siteName, String apiKey) {
         this(siteName, apiKey, null);
@@ -57,14 +59,22 @@ public static void configure(String siteName, String apikey) {
         Environment.defaultEnv = new Environment(siteName, apikey);
     }
     
-    public static void reqInterceptor(RequestInterceptor reqInterceptor) {
-        defaultConfig().reqInterceptor = reqInterceptor;
+    public void reqInterceptor(RequestInterceptor reqInterceptor) {
+	   this.reqInterceptor = reqInterceptor;
+    }
+
+    public void asyncReqInterceptor(AsyncRequestInterceptor asyncReqInterceptor) {
+        this.asyncReqInterceptor = asyncReqInterceptor;
     }
     
     public RequestInterceptor reqInterceptor() {
         return reqInterceptor;
     }
 
+    public AsyncRequestInterceptor asyncReqInterceptor() {
+        return asyncReqInterceptor;
+    }
+
     public static Environment defaultConfig() {
         if(defaultEnv == null) {
             throw new RuntimeException("The default environment has not been configured");
diff --git a/src/main/java/com/chargebee/internal/AsyncResult.java b/src/main/java/com/chargebee/internal/AsyncResult.java
new file mode 100644
index 00000000..93509a82
--- /dev/null
+++ b/src/main/java/com/chargebee/internal/AsyncResult.java
@@ -0,0 +1,4 @@
+package com.chargebee.internal;
+
+public interface AsyncResult {
+}
diff --git a/src/main/java/com/chargebee/internal/ListRequest.java b/src/main/java/com/chargebee/internal/ListRequest.java
index 3fae7057..b2e7d8c9 100644
--- a/src/main/java/com/chargebee/internal/ListRequest.java
+++ b/src/main/java/com/chargebee/internal/ListRequest.java
@@ -1,5 +1,6 @@
 package com.chargebee.internal;
 
+import com.chargebee.AsyncRequestWrap;
 import com.chargebee.RequestWrap;
 import com.chargebee.Environment;
 import com.chargebee.ListResult;
@@ -59,6 +60,14 @@ public ListResult call() throws Exception {
         return (ListResult) (env.reqInterceptor() != null ? env.reqInterceptor().handleRequest(c) : c.call());
 
     }
+
+    public final AsyncResult asyncRequest(Environment env) throws IOException, Exception {
+        if(env.asyncReqInterceptor() == null) {
+            throw new RuntimeException("Async Request interceptor cannot be null");
+        }
+        return env.asyncReqInterceptor().handleRequest(new AsyncRequestWrap(env, this, HttpUtil.Method.GET, this.uri));
+
+    }
     
     private static ListResult _request(Environment env, ListRequest req) throws IOException {
         if (env == null) {
diff --git a/src/main/java/com/chargebee/internal/Request.java b/src/main/java/com/chargebee/internal/Request.java
index 7e3f0729..f643dbff 100644
--- a/src/main/java/com/chargebee/internal/Request.java
+++ b/src/main/java/com/chargebee/internal/Request.java
@@ -33,6 +33,13 @@ public Result call() throws Exception {
         return (Result) (env.reqInterceptor() != null ? env.reqInterceptor().handleRequest(c) : c.call());
     }
 
+    public final AsyncResult asyncRequest(Environment env) throws Exception {
+        if(env.asyncReqInterceptor() == null) {
+            throw new RuntimeException("Async Request interceptor cannot be null");
+        }
+        return env.asyncReqInterceptor().handleRequest(new AsyncRequestWrap(env, this, this.httpMeth, this.uri));
+    }
+
     private static Result _request(Environment env, Request<?> req) throws IOException {
         if (env == null) {
             throw new RuntimeException("Environment cannot be null");
@@ -52,5 +59,4 @@ private static Result _request(Environment env, Request<?> req) throws IOExcepti
     public Params params() {
         return params;
     }
-    
 }
diff --git a/src/main/java/com/chargebee/internal/RequestBase.java b/src/main/java/com/chargebee/internal/RequestBase.java
index 55897eab..aa1f32ee 100644
--- a/src/main/java/com/chargebee/internal/RequestBase.java
+++ b/src/main/java/com/chargebee/internal/RequestBase.java
@@ -18,6 +18,10 @@ public Params params() {
         return params;
     }
 
+    public Map<String,String> headers() {
+        return headers;
+    }
+
     public U header(String headerName,String headerValue){        
         headers.put(headerName, headerValue);
         return (U)this;
diff --git a/src/main/java/com/chargebee/models/Invoice.java b/src/main/java/com/chargebee/models/Invoice.java
index fa4d768e..92c5087e 100644
--- a/src/main/java/com/chargebee/models/Invoice.java
+++ b/src/main/java/com/chargebee/models/Invoice.java
@@ -807,9 +807,9 @@ public static ChargeAddonRequest chargeAddon() throws IOException {
         return new ChargeAddonRequest(Method.POST, uri);
     }
 
-    public static Request stopDunning(String id) throws IOException {
+    public static StopDunningRequest stopDunning(String id) throws IOException {
         String uri = uri("invoices", nullCheck(id), "stop_dunning");
-        return new Request(Method.POST, uri);
+        return new StopDunningRequest(Method.POST, uri);
     }
 
     public static ImportInvoiceRequest importInvoice() throws IOException {
@@ -864,9 +864,9 @@ public static AddAddonChargeRequest addAddonCharge(String id) throws IOException
         return new AddAddonChargeRequest(Method.POST, uri);
     }
 
-    public static Request close(String id) throws IOException {
+    public static CloseRequest close(String id) throws IOException {
         String uri = uri("invoices", nullCheck(id), "close");
-        return new Request(Method.POST, uri);
+        return new CloseRequest(Method.POST, uri);
     }
 
     public static CollectPaymentRequest collectPayment(String id) throws IOException {
@@ -1217,6 +1217,24 @@ public Params params() {
         }
     }
 
+    public static class StopDunningRequest extends Request<StopDunningRequest> {
+
+        private StopDunningRequest(Method httpMeth, String uri) {
+            super(httpMeth, uri);
+        }
+    
+        public StopDunningRequest comment(String comment) {
+            params.addOpt("comment", comment);
+            return this;
+        }
+
+
+        @Override
+        public Params params() {
+            return params;
+        }
+    }
+    
     public static class ImportInvoiceRequest extends Request<ImportInvoiceRequest> {
 
         private ImportInvoiceRequest(Method httpMeth, String uri) {
@@ -1642,6 +1660,12 @@ private ApplyPaymentsRequest(Method httpMeth, String uri) {
             super(httpMeth, uri);
         }
     
+        public ApplyPaymentsRequest comment(String comment) {
+            params.addOpt("comment", comment);
+            return this;
+        }
+
+
         public ApplyPaymentsRequest transactionId(int index, String transactionId) {
             params.addOpt("transactions[id][" + index + "]", transactionId);
             return this;
@@ -1657,7 +1681,13 @@ public static class ApplyCreditsRequest extends Request<ApplyCreditsRequest> {
         private ApplyCreditsRequest(Method httpMeth, String uri) {
             super(httpMeth, uri);
         }
-    
+        
+        public ApplyCreditsRequest comment(String comment) {
+            params.addOpt("comment", comment);
+            return this;
+        }
+
+
         public ApplyCreditsRequest creditNoteId(int index, String creditNoteId) {
             params.addOpt("credit_notes[id][" + index + "]", creditNoteId);
             return this;
@@ -1838,6 +1868,10 @@ public AddChargeRequest avalaraServiceType(Integer avalaraServiceType) {
             return this;
         }
 
+        public AddChargeRequest comment(String comment) {
+            params.addOpt("comment", comment);
+            return this;
+        }
 
         public AddChargeRequest lineItemDateFrom(Timestamp lineItemDateFrom) {
             params.addOpt("line_item[date_from]", lineItemDateFrom);
@@ -1879,6 +1913,12 @@ public AddAddonChargeRequest addonUnitPrice(Integer addonUnitPrice) {
         }
 
 
+        public AddAddonChargeRequest comment(String comment) {
+            params.addOpt("comment", comment);
+            return this;
+        }
+
+
         public AddAddonChargeRequest lineItemDateFrom(Timestamp lineItemDateFrom) {
             params.addOpt("line_item[date_from]", lineItemDateFrom);
             return this;
@@ -1895,6 +1935,24 @@ public Params params() {
         }
     }
 
+    public static class CloseRequest extends Request<CloseRequest> {
+
+        private CloseRequest(Method httpMeth, String uri) {
+            super(httpMeth, uri);
+        }
+    
+        public CloseRequest comment(String comment) {
+            params.addOpt("comment", comment);
+            return this;
+        }
+
+
+        @Override
+        public Params params() {
+            return params;
+        }
+    }
+
     public static class CollectPaymentRequest extends Request<CollectPaymentRequest> {
 
         private CollectPaymentRequest(Method httpMeth, String uri) {
@@ -1919,6 +1977,12 @@ public CollectPaymentRequest paymentSourceId(String paymentSourceId) {
         }
 
 
+        public CollectPaymentRequest comment(String comment) {
+            params.addOpt("comment", comment);
+            return this;
+        }
+
+
         @Override
         public Params params() {
             return params;
@@ -2173,6 +2237,12 @@ public UpdateDetailsRequest poNumber(String poNumber) {
         }
 
 
+        public UpdateDetailsRequest comment(String comment) {
+            params.addOpt("comment", comment);
+            return this;
+        }
+
+
         public UpdateDetailsRequest billingAddressFirstName(String billingAddressFirstName) {
             params.addOpt("billing_address[first_name]", billingAddressFirstName);
             return this;