diff --git a/Xero.NetStandard.OAuth2/Client/ApiClient.cs b/Xero.NetStandard.OAuth2/Client/ApiClient.cs
index 39de7452..8abb3409 100644
--- a/Xero.NetStandard.OAuth2/Client/ApiClient.cs
+++ b/Xero.NetStandard.OAuth2/Client/ApiClient.cs
@@ -265,6 +265,43 @@ public ApiClient(string basePath)
             _baseUrl = basePath;
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ApiClient" />, defaulting to the global configurations' base url.
+        /// </summary>
+        /// <param name="client">An instance of HttpClient.</param>
+        /// <param name="handler">An optional instance of HttpClientHandler that is used by HttpClient.</param>
+        /// <exception cref="ArgumentNullException"></exception>
+        /// <remarks>
+        /// Some configuration settings will not be applied without passing an HttpClientHandler.
+        /// The features affected are: Setting and Retrieving Cookies, Client Certificates, Proxy settings.
+        /// </remarks>
+        public ApiClient(HttpClient client, HttpClientHandler handler = null) :
+                 this(client, Xero.NetStandard.OAuth2.Client.GlobalConfiguration.Instance.BasePath, handler)
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ApiClient" />.
+        /// </summary>
+        /// <param name="client">An instance of HttpClient.</param>
+        /// <param name="basePath">The target service's base path in URL format.</param>
+        /// <param name="handler">An optional instance of HttpClientHandler that is used by HttpClient.</param>
+        /// <exception cref="ArgumentNullException"></exception>
+        /// <exception cref="ArgumentException"></exception>
+        /// <remarks>
+        /// Some configuration settings will not be applied without passing an HttpClientHandler.
+        /// The features affected are: Setting and Retrieving Cookies, Client Certificates, Proxy settings.
+        /// </remarks>
+        public ApiClient(HttpClient client, string basePath, HttpClientHandler handler = null)
+        {
+            if (client == null) throw new ArgumentNullException("client cannot be null");
+            if (string.IsNullOrEmpty(basePath)) throw new ArgumentException("basePath cannot be empty");
+
+            _httpClientHandler = handler;
+            _httpClient = client;
+            _baseUrl = basePath;
+        }
+
         /// <summary>
         /// Disposes resources if they were created by us
         /// </summary>