diff --git a/CHANGELOG.md b/CHANGELOG.md
index e4bc2f5..67b60af 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changelog
 
+## 0.22.0 (16.08.2024)
+
+- Add hash to handle transaction timeout response. See [PR #374](https://github.com/kommitters/stellar_sdk/pull/374)
+- Add new async transaction submission endpoint. See [PR #373](https://github.com/kommitters/stellar_sdk/pull/373)
+
 ## 0.21.2 (23.07.2024)
 
 - Update stellar base dependency.
diff --git a/README.md b/README.md
index 23e8339..5713dd1 100644
--- a/README.md
+++ b/README.md
@@ -36,7 +36,7 @@ The **Stellar SDK** is composed of two complementary components: **`TxBuild`** +
 ```elixir
 def deps do
   [
-    {:stellar_sdk, "~> 0.21.2"}
+    {:stellar_sdk, "~> 0.22.0"}
   ]
 end
 ```
@@ -583,6 +583,9 @@ See [**Stellar.Horizon.Accounts**](https://hexdocs.pm/stellar_sdk/Stellar.Horizo
 # submit a transaction
 Stellar.Horizon.Transactions.create(Stellar.Horizon.Server.testnet(), base64_tx_envelope)
 
+# submit a transaction asynchronously
+Stellar.Horizon.Transactions.create_async(Stellar.Horizon.Server.testnet(), base64_tx_envelope)
+
 # retrieve a transaction
 Stellar.Horizon.Transactions.retrieve(Stellar.Horizon.Server.testnet(), "5ebd5c0af4385500b53dd63b0ef5f6e8feef1a7e1c86989be3cdcce825f3c0cc")
 
diff --git a/lib/horizon/ErrorMapper.ex b/lib/horizon/ErrorMapper.ex
new file mode 100644
index 0000000..9624427
--- /dev/null
+++ b/lib/horizon/ErrorMapper.ex
@@ -0,0 +1,30 @@
+defmodule Stellar.Horizon.ErrorMapper do
+  @moduledoc """
+  Assigns errors returned by the HTTP client to a custom structure.
+  """
+  alias Stellar.Horizon.AsyncTransactionError
+  alias Stellar.Horizon.AsyncTransaction
+  alias Stellar.Horizon.Error
+
+  @type error_source :: :horizon | :network
+  @type error_body :: map() | atom() | String.t()
+  @type error :: {error_source(), error_body()}
+
+  @type t :: {:error, struct()}
+
+  @spec build(error :: error()) :: t()
+  def build(
+        {:horizon,
+         %{hash: _hash, errorResultXdr: _error_result_xdr, tx_status: _tx_status} = decoded_body}
+      ) do
+    error = AsyncTransactionError.new(decoded_body)
+    {:error, error}
+  end
+
+  def build({:horizon, %{hash: _hash, tx_status: _tx_status} = decoded_body}) do
+    error = AsyncTransaction.new(decoded_body)
+    {:error, error}
+  end
+
+  def build(error), do: {:error, Error.new(error)}
+end
diff --git a/lib/horizon/asyncTransaction.ex b/lib/horizon/asyncTransaction.ex
new file mode 100644
index 0000000..8415173
--- /dev/null
+++ b/lib/horizon/asyncTransaction.ex
@@ -0,0 +1,24 @@
+defmodule Stellar.Horizon.AsyncTransaction do
+  @moduledoc """
+  Represents a `Asynchronous transaction` resource from Horizon API.
+  """
+
+  @behaviour Stellar.Horizon.Resource
+
+  alias Stellar.Horizon.Mapping
+
+  @type t :: %__MODULE__{
+          hash: String.t() | nil,
+          tx_status: String.t() | nil
+        }
+
+  defstruct [
+    :hash,
+    :tx_status
+  ]
+
+  @impl true
+  def new(attrs, opts \\ [])
+
+  def new(attrs, _opts), do: Mapping.build(%__MODULE__{}, attrs)
+end
diff --git a/lib/horizon/asyncTransactionError.ex b/lib/horizon/asyncTransactionError.ex
new file mode 100644
index 0000000..799a5dc
--- /dev/null
+++ b/lib/horizon/asyncTransactionError.ex
@@ -0,0 +1,26 @@
+defmodule Stellar.Horizon.AsyncTransactionError do
+  @moduledoc """
+  Represents a `Asynchronous transaction error` resource from Horizon API.
+  """
+
+  @behaviour Stellar.Horizon.Resource
+
+  alias Stellar.Horizon.Mapping
+
+  @type t :: %__MODULE__{
+          hash: String.t() | nil,
+          tx_status: String.t() | nil,
+          errorResultXdr: String.t() | nil
+        }
+
+  defstruct [
+    :hash,
+    :tx_status,
+    :errorResultXdr
+  ]
+
+  @impl true
+  def new(attrs, opts \\ [])
+
+  def new(attrs, _opts), do: Mapping.build(%__MODULE__{}, attrs)
+end
diff --git a/lib/horizon/client/default.ex b/lib/horizon/client/default.ex
index 52d7456..2077016 100644
--- a/lib/horizon/client/default.ex
+++ b/lib/horizon/client/default.ex
@@ -7,7 +7,7 @@ defmodule Stellar.Horizon.Client.Default do
 
   @behaviour Stellar.Horizon.Client.Spec
 
-  alias Stellar.Horizon.{Error, Server}
+  alias Stellar.Horizon.{ErrorMapper, Server}
 
   @type status :: pos_integer()
   @type headers :: [{binary(), binary()}, ...]
@@ -15,7 +15,7 @@ defmodule Stellar.Horizon.Client.Default do
   @type success_response :: {:ok, status(), headers(), body()}
   @type error_response :: {:error, status(), headers(), body()} | {:error, any()}
   @type client_response :: success_response() | error_response()
-  @type parsed_response :: {:ok, map()} | {:error, Error.t()}
+  @type parsed_response :: {:ok, map()} | {:error, struct()}
 
   @impl true
   def request(%Server{url: base_url}, method, path, headers \\ [], body \\ "", opts \\ []) do
@@ -34,13 +34,11 @@ defmodule Stellar.Horizon.Client.Default do
 
   defp handle_response({:ok, status, _headers, body}) when status >= 400 and status <= 599 do
     decoded_body = json_library().decode!(body, keys: :atoms)
-    error = Error.new({:horizon, decoded_body})
-    {:error, error}
+    ErrorMapper.build({:horizon, decoded_body})
   end
 
   defp handle_response({:error, reason}) do
-    error = Error.new({:network, reason})
-    {:error, error}
+    ErrorMapper.build({:network, reason})
   end
 
   @spec http_client() :: atom()
diff --git a/lib/horizon/error.ex b/lib/horizon/error.ex
index b0ae0dd..51c3e2e 100644
--- a/lib/horizon/error.ex
+++ b/lib/horizon/error.ex
@@ -9,14 +9,18 @@ defmodule Stellar.Horizon.Error do
   @type detail :: String.t() | nil
   @type base64_xdr :: String.t()
   @type result_code :: String.t()
+  @type hash :: String.t()
+
   @type result_codes :: %{
           optional(:transaction) => result_code(),
           optional(:operations) => list(result_code())
         }
   @type extras :: %{
+          optional(:hash) => hash(),
           optional(:envelope_xdr) => base64_xdr(),
           optional(:result_codes) => result_codes(),
-          optional(:result_xdr) => base64_xdr()
+          optional(:result_xdr) => base64_xdr(),
+          optional(:error) => detail()
         }
   @type error_source :: :horizon | :network
   @type error_body :: map() | atom() | String.t()
@@ -30,7 +34,13 @@ defmodule Stellar.Horizon.Error do
           extras: extras()
         }
 
-  defstruct [:type, :title, :status_code, :detail, extras: %{}]
+  defstruct [
+    :type,
+    :title,
+    :status_code,
+    :detail,
+    extras: %{}
+  ]
 
   @spec new(error :: error()) :: t()
   def new({:horizon, %{type: type, title: title, status: status_code, detail: detail} = error}) do
diff --git a/lib/horizon/request.ex b/lib/horizon/request.ex
index 715af0a..ce030db 100644
--- a/lib/horizon/request.ex
+++ b/lib/horizon/request.ex
@@ -11,7 +11,7 @@ defmodule Stellar.Horizon.Request do
   At a minimum, a request must have the endpoint and method specified to be valid.
   """
 
-  alias Stellar.Horizon.{Collection, Error, Server}
+  alias Stellar.Horizon.{Collection, Server}
   alias Stellar.Horizon.Client, as: Horizon
 
   @type server :: Server.t()
@@ -26,8 +26,8 @@ defmodule Stellar.Horizon.Request do
   @type opts :: Keyword.t()
   @type params :: Keyword.t()
   @type query_params :: list(atom())
-  @type response :: {:ok, map()} | {:error, Error.t()}
-  @type parsed_response :: {:ok, struct()} | {:error, Error.t()}
+  @type response :: {:ok, map()} | {:error, struct()}
+  @type parsed_response :: {:ok, struct()} | {:error, struct()}
 
   @type t :: %__MODULE__{
           method: method(),
diff --git a/lib/horizon/transactions.ex b/lib/horizon/transactions.ex
index 8a11ec5..2e9711e 100644
--- a/lib/horizon/transactions.ex
+++ b/lib/horizon/transactions.ex
@@ -12,15 +12,24 @@ defmodule Stellar.Horizon.Transactions do
   Horizon API reference: https://developers.stellar.org/api/resources/transactions/
   """
 
-  alias Stellar.Horizon.{Collection, Effect, Error, Operation, Transaction, Request, Server}
+  alias Stellar.Horizon.{
+    Collection,
+    Effect,
+    Operation,
+    Transaction,
+    AsyncTransaction,
+    Request,
+    Server
+  }
 
   @type server :: Server.t()
   @type hash :: String.t()
   @type options :: Keyword.t()
   @type resource :: Transaction.t() | Collection.t()
-  @type response :: {:ok, resource()} | {:error, Error.t()}
+  @type response :: {:ok, resource()} | {:error, struct()}
 
   @endpoint "transactions"
+  @endpoint_async "transactions_async"
 
   @doc """
   Creates a transaction to the Stellar network.
@@ -152,4 +161,26 @@ defmodule Stellar.Horizon.Transactions do
     |> Request.perform()
     |> Request.results(collection: {Operation, &list_operations(server, hash, &1)})
   end
+
+  @doc """
+    Creates a transaction to the Stellar network asynchronously.
+
+    ## Parameters:
+      * `server`: The Horizon server to query.
+      * `tx`: The base64-encoded XDR of the transaction.
+
+    ## Examples
+
+        iex> Transactions.create_async(Stellar.Horizon.Server.testnet(), "AAAAAgAAAACQcEK2yfQA9CHrX+2UMkRIb/1wzltKqHpbdIcJbp+b/QAAAGQAAiEYAAAAAQAAAAEAAAAAAAAAAAAAAABgXP3QAAAAAQAAABBUZXN0IFRyYW5zYWN0aW9uAAAAAQAAAAAAAAABAAAAAJBwQrbJ9AD0Ietf7ZQyREhv/XDOW0qoelt0hwlun5v9AAAAAAAAAAAF9eEAAAAAAAAAAAFun5v9AAAAQKdJnG8QRiv9xGp1Oq7ACv/xR2BnNqjfUHrGNua7m4tWbrun3+GmAj6ca3xz+4ZppWRTbvTUcCxvpbHERZ85QgY=")
+        {:ok, %AsyncTransaction{}}
+  """
+  @spec create_async(server :: server(), base64_envelope :: String.t()) :: response()
+  def create_async(server, base64_envelope) do
+    server
+    |> Request.new(:post, @endpoint_async)
+    |> Request.add_headers([{"Content-Type", "application/x-www-form-urlencoded"}])
+    |> Request.add_body(tx: base64_envelope)
+    |> Request.perform()
+    |> Request.results(as: AsyncTransaction)
+  end
 end
diff --git a/mix.exs b/mix.exs
index 73a3c9b..d2365ce 100644
--- a/mix.exs
+++ b/mix.exs
@@ -2,7 +2,7 @@ defmodule Stellar.MixProject do
   use Mix.Project
 
   @github_url "https://github.com/kommitters/stellar_sdk"
-  @version "0.21.2"
+  @version "0.22.0"
 
   def project do
     [
diff --git a/test/horizon/async_transaction_test.exs b/test/horizon/async_transaction_test.exs
new file mode 100644
index 0000000..d36e5e0
--- /dev/null
+++ b/test/horizon/async_transaction_test.exs
@@ -0,0 +1,28 @@
+defmodule Stellar.Horizon.AsyncTransactionTest do
+  use ExUnit.Case
+
+  alias Stellar.Test.Fixtures.Horizon
+
+  alias Stellar.Horizon.AsyncTransaction
+
+  setup do
+    json_body = Horizon.fixture("async_transaction")
+    attrs = Jason.decode!(json_body, keys: :atoms)
+
+    %{attrs: attrs}
+  end
+
+  test "new/2", %{attrs: attrs} do
+    %AsyncTransaction{
+      hash: "12958c37b341802a19ddada4c2a56b453a9cba728b2eefdfbc0b622e37379222",
+      tx_status: "PENDING"
+    } = AsyncTransaction.new(attrs)
+  end
+
+  test "new/2 empty_attrs" do
+    %AsyncTransaction{
+      hash: nil,
+      tx_status: nil
+    } = AsyncTransaction.new(%{})
+  end
+end
diff --git a/test/horizon/client/default_test.exs b/test/horizon/client/default_test.exs
index dfad977..22a2c71 100644
--- a/test/horizon/client/default_test.exs
+++ b/test/horizon/client/default_test.exs
@@ -104,8 +104,15 @@ defmodule Stellar.Horizon.Client.DefaultTest do
     end
 
     test "timeout", %{server: server} do
-      {:error, %Error{title: "Timeout", status_code: 504}} =
-        Default.request(server, :post, "/transactions?tx=timeout")
+      {:error,
+       %Error{
+         title: "Transaction Submission Timeout",
+         status_code: 504,
+         extras: %{
+           hash: _hash,
+           envelope_xdr: _envelope_xdr
+         }
+       }} = Default.request(server, :post, "/transactions?tx=timeout")
     end
 
     test "network_error", %{server: server} do
diff --git a/test/horizon/transactions_test.exs b/test/horizon/transactions_test.exs
index b748a9e..5084d96 100644
--- a/test/horizon/transactions_test.exs
+++ b/test/horizon/transactions_test.exs
@@ -4,7 +4,6 @@ defmodule Stellar.Horizon.Client.CannedTransactionRequests do
   alias Stellar.Test.Fixtures.Horizon
 
   @base_url "https://horizon-testnet.stellar.org"
-
   @spec request(
           method :: atom(),
           url :: String.t(),
@@ -91,6 +90,37 @@ defmodule Stellar.Horizon.Client.CannedTransactionRequests do
     json_body = Horizon.fixture("transaction")
     {:ok, 200, [], json_body}
   end
+
+  def request(
+        :post,
+        @base_url <> "/transactions_async",
+        _headers,
+        "tx=AAAAAgAAAABp0mQhoc0djMaRJSbxa417D7Lx8Dw%2ByWmvhALa5UuYkgAAAGQADk7SAAAAUQAAAAAAAAABAAAABE1FTU8AAAABAAAAAAAAAAEAAAAAv6Mnl0vbOahrXvJAay9nTrMHQ1pZcvYeA4wrv0xOeA4AAAAAAAAAAAL68IAAAAAAAAAAAA%3D%3D",
+        _opts
+      ) do
+    json_error = Horizon.fixture("400_async_transaction_error_result_xdr")
+    {:ok, 400, [], json_error}
+  end
+
+  def request(:post, @base_url <> "/transactions_async", _headers, "tx=tx_malformed", _opts) do
+    json_error = Horizon.fixture("400_transaction_malformed")
+    {:ok, 400, [], json_error}
+  end
+
+  def request(:post, @base_url <> "/transactions_async", _headers, "tx=duplicate", _opts) do
+    json_error = Horizon.fixture("409_async_transaction_duplicate")
+    {:ok, 409, [], json_error}
+  end
+
+  def request(:post, @base_url <> "/transactions_async", _headers, "tx=try_again_later", _opts) do
+    json_error = Horizon.fixture("409_async_transaction_try_again_later")
+    {:ok, 503, [], json_error}
+  end
+
+  def request(:post, @base_url <> "/transactions_async", _headers, "tx=" <> _envelope, _opts) do
+    json_body = Horizon.fixture("async_transaction")
+    {:ok, 201, [], json_body}
+  end
 end
 
 defmodule Stellar.Horizon.TransactionsTest do
@@ -104,6 +134,8 @@ defmodule Stellar.Horizon.TransactionsTest do
     Error,
     Operation,
     Transaction,
+    AsyncTransaction,
+    AsyncTransactionError,
     Transactions,
     Transaction.Preconditions,
     Transaction.TimeBounds,
@@ -120,11 +152,29 @@ defmodule Stellar.Horizon.TransactionsTest do
       Application.delete_env(:stellar_sdk, :http_client)
     end)
 
+    async_transaction_error = %{
+      # An erroneously generated base64_envelope may be generated when, e.g. the transaction is not signed.
+      bad_base64_envelope:
+        "AAAAAgAAAABp0mQhoc0djMaRJSbxa417D7Lx8Dw+yWmvhALa5UuYkgAAAGQADk7SAAAAUQAAAAAAAAABAAAABE1FTU8AAAABAAAAAAAAAAEAAAAAv6Mnl0vbOahrXvJAay9nTrMHQ1pZcvYeA4wrv0xOeA4AAAAAAAAAAAL68IAAAAAAAAAAAA==",
+      tx_status: "ERROR",
+      hash: "12958c37b341802a19ddada4c2a56b453a9cba728b2eefdfbc0b622e37379222",
+      errorResultXdr: "AAAAAAAAAGT////6AAAAAA=="
+    }
+
+    async_transaction = %{
+      base64_envelope:
+        "AAAAAgAAAABp0mQhoc0djMaRJSbxa417D7Lx8Dw+yWmvhALa5UuYkgAAAGQADk7SAAAAUQAAAAAAAAABAAAABE1FTU8AAAABAAAAAAAAAAEAAAAAv6Mnl0vbOahrXvJAay9nTrMHQ1pZcvYeA4wrv0xOeA4AAAAAAAAAAAL68IAAAAAAAAAAAeVLmJIAAABAk2E4qeHPsMKzj3kuCBoFC9stkVhOWpoJ3Fr5qf5zDu2eSz8blBi+4msu+PV8pg5e2MdymSOEBbPY2XLJcefRCw==",
+      tx_status: "PENDING",
+      hash: "12958c37b341802a19ddada4c2a56b453a9cba728b2eefdfbc0b622e37379222"
+    }
+
     %{
       source_account: "GCXMWUAUF37IWOOV2FRDKWEX3O2IHLM2FYH4WPI4PYUKAIFQEUU5X3TD",
       base64_envelope:
         "AAAAAJ2kP2xLaOVLj6DRwX1mMyA0mubYnYvu0g8OdoDqxXuFAAAAZADjfzAACzBMAAAAAQAAAAAAAAAAAAAAAF4vYIYAAAABAAAABjI5ODQyNAAAAAAAAQAAAAAAAAABAAAAAKdeYELovtcnTxqPEVsdbxHLMoMRalZsK7lo/+3ARzUZAAAAAAAAAADUFJPYAAAAAAAAAAHqxXuFAAAAQBpLpQyh+mwDd5nDSxTaAh5wopBBUaSD1eOK9MdiO+4kWKVTqSr/Ko3kYE/+J42Opsewf81TwINONPbY2CtPggE=",
-      hash: "132c440e984ab97d895f3477015080aafd6c4375f6a70a87327f7f95e13c4e31"
+      hash: "132c440e984ab97d895f3477015080aafd6c4375f6a70a87327f7f95e13c4e31",
+      async_transaction: async_transaction,
+      async_transaction_error: async_transaction_error
     }
   end
 
@@ -133,6 +183,16 @@ defmodule Stellar.Horizon.TransactionsTest do
       Transactions.create(Server.testnet(), base64_envelope)
   end
 
+  test "create_async/1", %{
+    async_transaction: %{base64_envelope: base64_envelope, hash: hash, tx_status: tx_status}
+  } do
+    {:ok,
+     %Stellar.Horizon.AsyncTransaction{
+       hash: ^hash,
+       tx_status: ^tx_status
+     }} = Transactions.create_async(Server.testnet(), base64_envelope)
+  end
+
   test "retrieve/1", %{
     hash: hash,
     base64_envelope: base64_envelope,
@@ -257,4 +317,49 @@ defmodule Stellar.Horizon.TransactionsTest do
        extras: %{result_codes: %{transaction: "tx_insufficient_fee"}}
      }} = Transactions.create(Server.testnet(), "bad")
   end
+
+  test "malformed async transaction error" do
+    {:error,
+     %Error{
+       type: "https://stellar.org/horizon-errors/transaction_malformed",
+       title: "Transaction Malformed",
+       status_code: 400,
+       detail: _detail,
+       extras: %{envelope_xdr: "tx_malformed", error: %{}}
+     }} = Transactions.create_async(Server.testnet(), "tx_malformed")
+  end
+
+  test "async transaction duplicate" do
+    # This happens when the same request is sent twice in a row to enpoint ‘transaction_async’.
+    {:error,
+     %AsyncTransaction{
+       hash: "822a283337b124f82b0b8725b39738d2f3e86b699e25b9b646809336384bf41c",
+       tx_status: "DUPLICATE"
+     }} = Transactions.create_async(Server.testnet(), "duplicate")
+  end
+
+  test "async transaction try_again_later" do
+    # This happens when the same request is spammed multiple times to enpoint ‘transaction_async’.
+    {:error,
+     %AsyncTransaction{
+       hash: "822a283337b124f82b0b8725b39738d2f3e86b699e25b9b646809336384bf41c",
+       tx_status: "TRY_AGAIN_LATER"
+     }} = Transactions.create_async(Server.testnet(), "try_again_later")
+  end
+
+  test "async transaction errorResultXdr", %{
+    async_transaction_error: %{
+      bad_base64_envelope: bad_base64_envelope,
+      hash: hash,
+      tx_status: tx_status,
+      errorResultXdr: error_result_xdr
+    }
+  } do
+    {:error,
+     %AsyncTransactionError{
+       hash: ^hash,
+       tx_status: ^tx_status,
+       errorResultXdr: ^error_result_xdr
+     }} = Transactions.create_async(Server.testnet(), bad_base64_envelope)
+  end
 end
diff --git a/test/support/fixtures/horizon/400_async_transaction_error_result_xdr.json b/test/support/fixtures/horizon/400_async_transaction_error_result_xdr.json
new file mode 100644
index 0000000..dce75c8
--- /dev/null
+++ b/test/support/fixtures/horizon/400_async_transaction_error_result_xdr.json
@@ -0,0 +1,5 @@
+{
+  "errorResultXdr": "AAAAAAAAAGT////6AAAAAA==",
+  "tx_status": "ERROR",
+  "hash": "12958c37b341802a19ddada4c2a56b453a9cba728b2eefdfbc0b622e37379222"
+}
diff --git a/test/support/fixtures/horizon/400_transaction_malformed.json b/test/support/fixtures/horizon/400_transaction_malformed.json
new file mode 100644
index 0000000..97f358d
--- /dev/null
+++ b/test/support/fixtures/horizon/400_transaction_malformed.json
@@ -0,0 +1,10 @@
+{
+  "type": "https://stellar.org/horizon-errors/transaction_malformed",
+  "title": "Transaction Malformed",
+  "status": 400,
+  "detail": "Horizon could not decode the transaction envelope in this request. A transaction should be an XDR TransactionEnvelope struct encoded using base64.  The envelope read from this request is echoed in the `extras.envelope_xdr` field of this response for your convenience.",
+  "extras": {
+    "envelope_xdr": "tx_malformed",
+    "error": {}
+  }
+}
diff --git a/test/support/fixtures/horizon/409_async_transaction_duplicate.json b/test/support/fixtures/horizon/409_async_transaction_duplicate.json
new file mode 100644
index 0000000..ed37760
--- /dev/null
+++ b/test/support/fixtures/horizon/409_async_transaction_duplicate.json
@@ -0,0 +1,4 @@
+{
+  "tx_status": "DUPLICATE",
+  "hash": "822a283337b124f82b0b8725b39738d2f3e86b699e25b9b646809336384bf41c"
+}
diff --git a/test/support/fixtures/horizon/409_async_transaction_try_again_later.json b/test/support/fixtures/horizon/409_async_transaction_try_again_later.json
new file mode 100644
index 0000000..0804f1c
--- /dev/null
+++ b/test/support/fixtures/horizon/409_async_transaction_try_again_later.json
@@ -0,0 +1,4 @@
+{
+  "tx_status": "TRY_AGAIN_LATER",
+  "hash": "822a283337b124f82b0b8725b39738d2f3e86b699e25b9b646809336384bf41c"
+}
diff --git a/test/support/fixtures/horizon/504.json b/test/support/fixtures/horizon/504.json
index ac18995..20627c2 100644
--- a/test/support/fixtures/horizon/504.json
+++ b/test/support/fixtures/horizon/504.json
@@ -1,6 +1,10 @@
 {
-  "type": "https://stellar.org/horizon-errors/timeout",
-  "title": "Timeout",
+  "type": "https://developers.stellar.org/docs/data/horizon/api-reference/errors/http-status-codes/horizon-specific/timeout",
+  "title": "Transaction Submission Timeout",
   "status": 504,
-  "detail": "Your request timed out before completing.  Please try your request again. If you are submitting a transaction make sure you are sending exactly the same transaction (with the same sequence number)."
+  "detail": "Your transaction submission request has timed out. This does not necessarily mean the submission has failed. Before resubmitting, please use the transaction hash provided in `extras.hash` to poll the GET /transactions endpoint for sometime and check if it was included in a ledger.",
+  "extras": {
+    "hash": "12958c37b341802a19ddada4c2a56b453a9cba728b2eefdfbc0b622e37379222",
+    "envelope_xdr": "AAAAAJ2kP2xLaOVLj6DRwX1mMyA0mubYnYvu0g8OdoDqxXuFAAAAZADjfzAACzBMAAAAAQAAAAAAAAAAAAAAAF4vYIYAAAABAAAABjI5ODQyNAAAAAAAAQAAAAAAAAABAAAAAKdeYELovtcnTxqPEVsdbxHLMoMRalZsK7lo/+3ARzUZAAAAAAAAAADUFJPYAAAAAAAAAAHqxXuFAAAAQBpLpQyh+mwDd5nDSxTaAh5wopBBUaSD1eOK9MdiO+4kWKVTqSr/Ko3kYE/+J42Opsewf81TwINONPbY2CtPggE="
+  }
 }
diff --git a/test/support/fixtures/horizon/async_transaction.json b/test/support/fixtures/horizon/async_transaction.json
new file mode 100644
index 0000000..188e561
--- /dev/null
+++ b/test/support/fixtures/horizon/async_transaction.json
@@ -0,0 +1,4 @@
+{
+   "tx_status": "PENDING",
+   "hash": "12958c37b341802a19ddada4c2a56b453a9cba728b2eefdfbc0b622e37379222"
+}