diff --git a/src/Todoist.Net.Tests/Services/ItemsServiceTests.cs b/src/Todoist.Net.Tests/Services/ItemsServiceTests.cs
index 68eba51..242d630 100644
--- a/src/Todoist.Net.Tests/Services/ItemsServiceTests.cs
+++ b/src/Todoist.Net.Tests/Services/ItemsServiceTests.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Linq;
+using System.Threading.Tasks;
 
 using Todoist.Net.Exceptions;
 using Todoist.Net.Models;
@@ -125,7 +126,7 @@ public void CreateItem_InvalidPDueDate_ThrowsException()
 
         [Fact]
         [Trait(Constants.TraitName, Constants.IntegrationFreeTraitValue)]
-        public void MoveItemsToProject_Success()
+        public async Task MoveItemsToProject_Success()
         {
             var client = TodoistClientFactory.Create(_outputHelper);
 
@@ -133,22 +134,22 @@ public void MoveItemsToProject_Success()
             client.Items.AddAsync(item).Wait();
 
             item.DueDate = new DueDate("every fri");
-            client.Items.UpdateAsync(item).Wait();
+            await client.Items.UpdateAsync(item);
 
             var project = new Project(Guid.NewGuid().ToString());
-            client.Projects.AddAsync(project).Wait();
+            await client.Projects.AddAsync(project);
 
-            var itemInfo = client.Items.GetAsync(item.Id).Result;
+            var itemInfo = await client.Items.GetAsync(item.Id);
 
             Assert.True(project.Id != itemInfo.Project.Id);
 
-            client.Items.MoveAsync(ItemMoveArgument.CreateMoveToProject(itemInfo.Item.Id, project.Id)).Wait();
-            itemInfo = client.Items.GetAsync(itemInfo.Item.Id).Result;
+            await client.Items.MoveAsync(ItemMoveArgument.CreateMoveToProject(itemInfo.Item.Id, project.Id));
+            itemInfo = await client.Items.GetAsync(itemInfo.Item.Id);
 
             Assert.True(project.Id == itemInfo.Project.Id);
 
-            client.Projects.DeleteAsync(project.Id).Wait();
-            client.Items.DeleteAsync(itemInfo.Item.Id).Wait();
+            await client.Items.DeleteAsync(itemInfo.Item.Id);
+            await client.Projects.DeleteAsync(project.Id);
         }
 
         [Fact]
diff --git a/src/Todoist.Net.Tests/Services/UsersServiceTests.cs b/src/Todoist.Net.Tests/Services/UsersServiceTests.cs
index fc61602..645d1dd 100644
--- a/src/Todoist.Net.Tests/Services/UsersServiceTests.cs
+++ b/src/Todoist.Net.Tests/Services/UsersServiceTests.cs
@@ -1,7 +1,5 @@
-using System;
 using System.Threading.Tasks;
 
-using Todoist.Net.Models;
 using Todoist.Net.Tests.Extensions;
 
 using Xunit;
@@ -30,31 +28,5 @@ public async Task GetCurrentAsync_Success()
             Assert.NotNull(user);
             Assert.NotNull(user.Id);
         }
-
-        [Fact]
-        [Trait(Constants.TraitName, Constants.IntegrationFreeTraitValue)]
-        public async Task RegisterUpdateSettingsAndDeleteUser_Success()
-        {
-            var todoistTokenlessClient = TodoistClientFactory.CreateTokenlessClient();
-
-            const string password = "Pa$$W@rd";
-            var userBase = new UserBase(Guid.NewGuid().ToString("N") + "@example.com", "test user", password);
-            var userInfo = await todoistTokenlessClient.RegisterUserAsync(userBase);
-            Assert.NotNull(userInfo);
-
-            var todoistClient = await todoistTokenlessClient.LoginAsync(userBase.Email, userBase.Password);
-            await todoistClient.Users.UpdateKarmaGoalsAsync(new KarmaGoals() { KarmaDisabled = true });
-
-            if (userInfo.HasPassword)
-            {
-                userInfo.CurrentPassword = password;
-            }
-
-            await todoistClient.Users.UpdateAsync(userInfo);
-
-            await todoistClient.Users.DeleteAsync(userBase.Password, "test");
-
-            todoistClient.Dispose();
-        }
     }
 }
diff --git a/src/Todoist.Net.Tests/TodoistClientFactory.cs b/src/Todoist.Net.Tests/TodoistClientFactory.cs
index e63527e..6ac48c0 100644
--- a/src/Todoist.Net.Tests/TodoistClientFactory.cs
+++ b/src/Todoist.Net.Tests/TodoistClientFactory.cs
@@ -11,10 +11,5 @@ public static ITodoistClient Create(ITestOutputHelper outputHelper)
             var token = SettingsProvider.GetToken();
             return new TodoistClient(new RateLimitAwareRestClient(token, outputHelper));
         }
-
-        public static ITodoistTokenlessClient CreateTokenlessClient()
-        {
-            return new TodoistTokenlessClient();
-        }
     }
 }
diff --git a/src/Todoist.Net/ITodoistTokenlessClient.cs b/src/Todoist.Net/ITodoistTokenlessClient.cs
deleted file mode 100644
index 2f82a7c..0000000
--- a/src/Todoist.Net/ITodoistTokenlessClient.cs
+++ /dev/null
@@ -1,64 +0,0 @@
-using System;
-using System.Net.Http;
-using System.Threading;
-using System.Threading.Tasks;
-
-using Todoist.Net.Exceptions;
-using Todoist.Net.Models;
-
-namespace Todoist.Net
-{
-    /// <summary>
-    /// A Todoist client without an access token.
-    /// </summary>
-    public interface ITodoistTokenlessClient
-    {
-        /// <summary>
-        /// Logins user and returns a new instance of Todoist client.
-        /// </summary>
-        /// <param name="email">The email.</param>
-        /// <param name="password">The password.</param>
-        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
-        /// <returns>
-        /// A new instance of Todoist client.
-        /// </returns>
-        /// <exception cref="ArgumentException">
-        /// Value cannot be null or empty. - email
-        /// or
-        /// Value cannot be null or empty. - password
-        /// </exception>
-        /// <exception cref="HttpRequestException">API exception.</exception>
-        /// <exception cref="TodoistException">Unable to get token.</exception>
-        Task<TodoistClient> LoginAsync(string email, string password, CancellationToken cancellationToken = default);
-
-        /// <summary>
-        /// Logins user and returns a new instance of Todoist client.
-        /// </summary>
-        /// <param name="email">The email.</param>
-        /// <param name="oauthToken">The oauth token.</param>
-        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
-        /// <returns>
-        /// A new instance of Todoist client.
-        /// </returns>
-        /// <exception cref="ArgumentException">
-        /// Value cannot be null or empty. - email
-        /// or
-        /// Value cannot be null or empty. - oauthToken
-        /// </exception>
-        /// <exception cref="TodoistException">API exception.</exception>
-        /// <exception cref="HttpRequestException">API exception.</exception>
-        Task<TodoistClient> LoginWithGoogleAsync(string email, string oauthToken, CancellationToken cancellationToken = default);
-
-        /// <summary>
-        /// Registers a new user.
-        /// </summary>
-        /// <param name="user">The user.</param>
-        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
-        /// <returns>
-        /// The user info.
-        /// </returns>
-        /// <exception cref="ArgumentNullException"><paramref name="user" /> is <see langword="null" /></exception>
-        /// <exception cref="HttpRequestException">API exception.</exception>
-        Task<UserInfo> RegisterUserAsync(UserBase user, CancellationToken cancellationToken = default);
-    }
-}
diff --git a/src/Todoist.Net/Todoist.Net.csproj b/src/Todoist.Net/Todoist.Net.csproj
index 76fe1e9..67bad49 100644
--- a/src/Todoist.Net/Todoist.Net.csproj
+++ b/src/Todoist.Net/Todoist.Net.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <Description>A Todoist API client for .NET</Description>
-    <VersionPrefix>5.1.0</VersionPrefix>
+    <VersionPrefix>6.0.0</VersionPrefix>
     <Authors>Oleg Shevchenko</Authors>
     <TargetFrameworks>netstandard2.0;net45</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
diff --git a/src/Todoist.Net/TodoistClient.cs b/src/Todoist.Net/TodoistClient.cs
index c891211..914aa9e 100644
--- a/src/Todoist.Net/TodoistClient.cs
+++ b/src/Todoist.Net/TodoistClient.cs
@@ -200,7 +200,7 @@ public void Dispose()
         /// <inheritdoc/>
         public Task<Resources> GetResourcesAsync(params ResourceType[] resourceTypes) =>
             GetResourcesAsync("*", resourceTypes);
-        
+
         /// <inheritdoc/>
         public Task<Resources> GetResourcesAsync(CancellationToken cancellationToken, params ResourceType[] resourceTypes) =>
             GetResourcesAsync("*", cancellationToken, resourceTypes);
diff --git a/src/Todoist.Net/TodoistTokenlessClient.cs b/src/Todoist.Net/TodoistTokenlessClient.cs
deleted file mode 100644
index cb1dca7..0000000
--- a/src/Todoist.Net/TodoistTokenlessClient.cs
+++ /dev/null
@@ -1,138 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Net;
-using System.Net.Http;
-using System.Threading;
-using System.Threading.Tasks;
-
-using Todoist.Net.Exceptions;
-using Todoist.Net.Models;
-
-namespace Todoist.Net
-{
-    /// <summary>
-    /// A Todoist client without an access token.
-    /// </summary>
-    /// <seealso cref="Todoist.Net.ITodoistTokenlessClient" />
-    /// <seealso cref="System.IDisposable" />
-    public sealed class TodoistTokenlessClient : ITodoistTokenlessClient, IDisposable
-    {
-        private readonly TodoistClient _todoistClient;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="TodoistTokenlessClient" /> class.
-        /// </summary>
-        public TodoistTokenlessClient() : this(new TodoistRestClient())
-        {
-        }
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="TodoistTokenlessClient" /> class.
-        /// </summary>
-        /// <param name="proxy">The proxy.</param>
-        public TodoistTokenlessClient(IWebProxy proxy) : this(new TodoistRestClient(proxy))
-        {
-        }
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="TodoistTokenlessClient" /> class.
-        /// </summary>
-        /// <param name="restClient">The rest client.</param>
-        public TodoistTokenlessClient(ITodoistRestClient restClient)
-        {
-            _todoistClient = new TodoistClient(restClient);
-        }
-
-        /// <summary>
-        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
-        /// </summary>
-        public void Dispose()
-        {
-            _todoistClient?.Dispose();
-        }
-
-        /// <inheritdoc/>
-        [Obsolete("This method is scheduled for deprecation and probably will be removed in future versions.")]
-        public Task<TodoistClient> LoginAsync(string email, string password, CancellationToken cancellationToken = default)
-        {
-            if (string.IsNullOrEmpty(email))
-            {
-                throw new ArgumentException("Value cannot be null or empty.", nameof(email));
-            }
-
-            if (string.IsNullOrEmpty(password))
-            {
-                throw new ArgumentException("Value cannot be null or empty.", nameof(password));
-            }
-
-            var parameters = new[]
-                                 {
-                                     new KeyValuePair<string, string>("email", email),
-                                     new KeyValuePair<string, string>("password", password)
-                                 };
-
-            return LoginWithCredentialsAsync("login", parameters, cancellationToken);
-        }
-
-        /// <inheritdoc/>
-        [Obsolete("This method is scheduled for deprecation and probably will be removed in future versions.")]
-        public Task<TodoistClient> LoginWithGoogleAsync(string email, string oauthToken, CancellationToken cancellationToken = default)
-        {
-            if (string.IsNullOrEmpty(email))
-            {
-                throw new ArgumentException("Value cannot be null or empty.", nameof(email));
-            }
-
-            if (string.IsNullOrEmpty(oauthToken))
-            {
-                throw new ArgumentException("Value cannot be null or empty.", nameof(oauthToken));
-            }
-
-            var parameters = new[]
-                                 {
-                                     new KeyValuePair<string, string>("email", email),
-                                     new KeyValuePair<string, string>("oauth2_token", oauthToken)
-                                 };
-
-            return LoginWithCredentialsAsync("login_with_google", parameters, cancellationToken);
-        }
-
-        /// <inheritdoc/>
-        public async Task<UserInfo> RegisterUserAsync(UserBase user, CancellationToken cancellationToken = default)
-        {
-            if (user == null)
-            {
-                throw new ArgumentNullException(nameof(user));
-            }
-
-            var userInfo = await ((IAdvancedTodoistClient)_todoistClient)
-                               .ProcessPostAsync<UserInfo>("user/register", user.ToParameters(), cancellationToken)
-                               .ConfigureAwait(false);
-
-            return userInfo;
-        }
-
-        /// <summary>
-        /// Logins with credentials and returns a new instance of Todoist client.
-        /// </summary>
-        /// <param name="resource">The resource.</param>
-        /// <param name="parameters">The parameters.</param>
-        /// <param name="cancellationToken">A cancellation token that can be used by other objects or threads to receive notice of cancellation.</param>
-        /// <returns>
-        /// A new instance of Todoist client.
-        /// </returns>
-        /// <exception cref="HttpRequestException">API exception.</exception>
-        /// <exception cref="TodoistException">Unable to get token.</exception>
-        private async Task<TodoistClient> LoginWithCredentialsAsync(
-            string resource,
-            KeyValuePair<string, string>[] parameters,
-            CancellationToken cancellationToken)
-        {
-            var userInfo = await ((IAdvancedTodoistClient)_todoistClient)
-                               .ProcessPostAsync<UserInfo>(resource, parameters, cancellationToken)
-                               .ConfigureAwait(false);
-
-            return new TodoistClient(userInfo.Token);
-        }
-    }
-}