diff --git a/Shippo/CustomsDeclaration.cs b/Shippo/CustomsDeclaration.cs
index 2c04ca2..dc56e71 100644
--- a/Shippo/CustomsDeclaration.cs
+++ b/Shippo/CustomsDeclaration.cs
@@ -27,6 +27,19 @@ public class ExporterIdentification : ShippoId
     {
         [JsonProperty(PropertyName = "eori_number")]
         public object EoriNumber { get; set; }
+
+        [JsonProperty(PropertyName = "tax_id")]
+        public TaxId TaxId { get; set; }
+    }
+
+    [JsonObject(MemberSerialization.OptIn)]
+    public class TaxId : ShippoId
+    {
+        [JsonProperty(PropertyName = "number")]
+        public object Number { get; set; }
+
+        [JsonProperty(PropertyName = "type")]
+        public object Type { get; set; }
     }
 
     [JsonObject(MemberSerialization.OptIn)]
diff --git a/ShippoTesting/CustomsDeclarationTest.cs b/ShippoTesting/CustomsDeclarationTest.cs
index cb3466a..ef94dc3 100644
--- a/ShippoTesting/CustomsDeclarationTest.cs
+++ b/ShippoTesting/CustomsDeclarationTest.cs
@@ -42,7 +42,10 @@ public void TestValidCreate()
             Assert.AreEqual(invoicedChargesParameters["other_fees"], testObject.InvoicedCharges.OtherFees);
             Assert.AreEqual(invoicedChargesParameters["currency"], testObject.InvoicedCharges.Currency);
 
-            var exporterIdentificationParameters = (Dictionary<String, String>)parameters["exporter_identification"];
+            var exporterIdentificationParameters = (Dictionary<String, Object>)parameters["exporter_identification"];
+            var taxIdParameters = (Dictionary<String, String>) exporterIdentificationParameters["tax_id"];
+            Assert.AreEqual(taxIdParameters["number"], testObject.ExporterIdentification.TaxId.Number);
+            Assert.AreEqual(taxIdParameters["type"], testObject.ExporterIdentification.TaxId.Type);
             Assert.AreEqual(exporterIdentificationParameters["eori_number"], testObject.ExporterIdentification.EoriNumber);
         }
 
@@ -114,8 +117,14 @@ public static Hashtable getDefaultParameters()
             };
             parameters.Add("invoiced_charges", invoicedCharges);
 
-            var exporterIdentification = new Dictionary<String, String>(){
+            var taxId = new Dictionary<String, String>()
+            {
+                {"number", "123456789"},
+                {"type", "EIN" }
+            };
+            var exporterIdentification = new Dictionary<String, Object>(){
                 {"eori_number", "PL12345678912345"},
+                {"tax_id", taxId}
             };
             parameters.Add("exporter_identification", exporterIdentification);