diff --git a/CHANGELOG.md b/CHANGELOG.md
index b0be8d0..152cea6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,9 @@ Given a version number MAJOR.MINOR.PATCH, increment:
 
 
 ## [Unreleased]
+### Added
+- Transfer.account_type property to allow "checking", "salary" or "savings" account specification
+- Transfer.external_id property to allow users to take control over duplication filters
 
 ## [2.3.0] - 2021-01-19
 ### Fixed
diff --git a/README.md b/README.md
index 3a7c3be..ec12e0b 100644
--- a/README.md
+++ b/README.md
@@ -304,6 +304,8 @@ transfers = StarkBank.Transfer.create!(
         bank_code: "341",  # TED
         branch_code: "1234",
         account_number: "123456-7",
+        account_type: "salary",
+        external_id: "my-internal-id-12345",
         tax_id: "012.345.678-90",
         name: "Jon Snow",
         scheduled: Date.utc_today |> Date.add(30)
diff --git a/lib/boleto_payment/boleto_payment.ex b/lib/boleto_payment/boleto_payment.ex
index 0dc60fd..5b7a547 100644
--- a/lib/boleto_payment/boleto_payment.ex
+++ b/lib/boleto_payment/boleto_payment.ex
@@ -144,7 +144,7 @@ defmodule StarkBank.BoletoPayment do
     - `:after` [Date or string, default nil]: date filter for structs created only after specified date. ex: ~D[2020-03-25]
     - `:before` [Date or string, default nil]: date filter for structs created only before specified date. ex: ~D[2020-03-25]
     - `:tags` [list of strings, default nil]: tags to filter retrieved structs. ex: ["tony", "stark"]
-    - `:ids` [list of strings, default null]: list of ids to filter retrieved objects. ex: ["5656565656565656", "4545454545454545"]
+    - `:ids` [list of strings, default nil]: list of ids to filter retrieved objects. ex: ["5656565656565656", "4545454545454545"]
     - `:status` [string, default nil]: filter for status of retrieved structs. ex: "paid"
     - `:user` [Organization/Project]: Organization or Project struct returned from StarkBank.project(). Only necessary if default project or organization has not been set in configs.
 
diff --git a/lib/brcode_payment/brcode_payment.ex b/lib/brcode_payment/brcode_payment.ex
index f5c6db9..3b74a43 100644
--- a/lib/brcode_payment/brcode_payment.ex
+++ b/lib/brcode_payment/brcode_payment.ex
@@ -31,7 +31,7 @@ defmodule StarkBank.BrcodePayment do
     - `:id` [string, default nil]: unique id returned when payment is created. ex: "5656565656565656"
     - `:name` [string, default nil]: receiver name. ex: "Jon Snow"
     - `:status` [string, default nil]: current payment status. ex: "success" or "failed"
-    - `:type` [string, default null]: brcode type. ex: "static" or "dynamic"
+    - `:type` [string, default nil]: brcode type. ex: "static" or "dynamic"
     - `:fee` [integer, default nil]: fee charged when a brcode payment is created. ex: 200 (= R$ 2.00)
     - `:created` [DateTime, default nil]: creation datetime for the payment. ex: ~U[2020-03-26 19:32:35.418698Z]
     - `:updated` [DateTime, default nil]: latest update datetime for the Deposit. ex: ~U[2020-08-20 19:32:35.418698Z]
@@ -147,7 +147,7 @@ defmodule StarkBank.BrcodePayment do
     - `:after` [Date or string, default nil]: date filter for structs created only after specified date. ex: ~D[2020-03-25]
     - `:before` [Date or string, default nil]: date filter for structs created only before specified date. ex: ~D[2020-03-25]
     - `:tags` [list of strings, default nil]: tags to filter retrieved structs. ex: ["tony", "stark"]
-    - `:ids` [list of strings, default null]: list of ids to filter retrieved objects. ex: ["5656565656565656", "4545454545454545"]
+    - `:ids` [list of strings, default nil]: list of ids to filter retrieved objects. ex: ["5656565656565656", "4545454545454545"]
     - `:status` [string, default nil]: filter for status of retrieved structs. ex: "paid"
     - `:user` [Organization/Project]: Organization or Project struct returned from StarkBank.project(). Only necessary if default project or organization has not been set in configs.
 
diff --git a/lib/dict_key/dict_key.ex b/lib/dict_key/dict_key.ex
index c05ee54..69b3a84 100644
--- a/lib/dict_key/dict_key.ex
+++ b/lib/dict_key/dict_key.ex
@@ -27,8 +27,8 @@ defmodule StarkBank.DictKey do
     - `:account_type` [string, default nil]: bank account type associated with the DICT key. ex: "checking", "saving" e "salary"
     - `:status` [string, default nil]: current DICT key status. ex: "created", "registered", "canceled" or "failed"
     - `:account_created` [datetime.datetime, default nil]: creation datetime of the bank account associated with the DICT key. ex: datetime.date(2020, 1, 12, 11, 14, 8)
-    - `:owned` [DateTime, default null]: datetime since when the current owner hold this DICT key. ex: ~U[2020-11-26 17:31:45.482618Z]
-    - `:created` [DateTime, default null]: creation datetime for the DICT key. ex: ~U[2020-11-26 17:31:45.482618Z]
+    - `:owned` [DateTime, default nil]: datetime since when the current owner hold this DICT key. ex: ~U[2020-11-26 17:31:45.482618Z]
+    - `:created` [DateTime, default nil]: creation datetime for the DICT key. ex: ~U[2020-11-26 17:31:45.482618Z]
   """
   defstruct [
     :id,
@@ -81,7 +81,7 @@ defmodule StarkBank.DictKey do
     - `:type` [string, default nil]: DictKey type. ex: "cpf", "cnpj", "phone", "email" or "evp"
     - `:after` [Date or string, default nil]: date filter for structs created only after specified date. ex: ~D[2020-03-25]
     - `:before` [Date or string, default nil]: date filter for structs created only before specified date. ex: ~D[2020-03-25]
-    - `:ids` [list of strings, default null]: list of ids to filter retrieved objects. ex: ["5656565656565656", "4545454545454545"]
+    - `:ids` [list of strings, default nil]: list of ids to filter retrieved objects. ex: ["5656565656565656", "4545454545454545"]
     - `:status` [string, default nil]: filter for status of retrieved structs. ex: "registered"
     - `:user` [Organization/Project]: Organization or Project struct returned from StarkBank.project(). Only necessary if default project or organization has not been set in configs.
 
diff --git a/lib/starkbank.ex b/lib/starkbank.ex
index 232df61..307e05b 100644
--- a/lib/starkbank.ex
+++ b/lib/starkbank.ex
@@ -59,7 +59,7 @@ defmodule StarkBank do
     - `:private_key` [EllipticCurve.Organization()]: PEM string of the private key linked to the organization. ex: "-----BEGIN PUBLIC KEY-----\nMFYwEAYHKoZIzj0CAQYFK4EEAAoDQgAEyTIHK6jYuik6ktM9FIF3yCEYzpLjO5X/\ntqDioGM+R2RyW0QEo+1DG8BrUf4UXHSvCjtQ0yLppygz23z0yPZYfw==\n-----END PUBLIC KEY-----"
 
   ## Parameters (optional):
-    - `:workspace_id` [string]: unique id of the accessed Workspace, if any. ex: None or "4848484848484848"
+    - `:workspace_id` [string]: unique id of the accessed Workspace, if any. ex: nil or "4848484848484848"
   """
   @spec organization(
           environment: :production | :sandbox,
diff --git a/lib/transfer/transfer.ex b/lib/transfer/transfer.ex
index 26ed61d..4e6634e 100644
--- a/lib/transfer/transfer.ex
+++ b/lib/transfer/transfer.ex
@@ -21,11 +21,13 @@ defmodule StarkBank.Transfer do
     - `:tax_id` [string]: receiver tax ID (CPF or CNPJ) with or without formatting. ex: "01234567890" or "20.018.183/0001-80"
     - `:bank_code` [string]: code of the receiver bank institution in Brazil. If an ISPB (8 digits) is informed, a PIX transfer will be created, else a TED will be issued. ex: "20018183" or "341"
     - `:branch_code` [string]: receiver bank account branch. Use '-' in case there is a verifier digit. ex: "1357-9"
-    - `:account_number` [string]: Receiver Bank Account number. Use '-' before the verifier digit. ex: "876543-2"
+    - `:account_number` [string]: Receiver bank account number. Use '-' before the verifier digit. ex: "876543-2"
 
   ## Parameters (optional):
-    - `:tags` [list of strings]: list of strings for reference when searching for transfers. ex: ["employees", "monthly"]
+    - `:account_type` [string, default "checking"]: Receiver bank account type. This parameter only has effect on Pix Transfers. ex: "checking", "savings" or "salary"
+    - `:external_id` [string, default nil]: url safe string that must be unique among all your transfers. Duplicated external_ids will cause failures. By default, this parameter will block any transfer that repeats amount and receiver information on the same date. ex: "my-internal-id-123456"
     - `:scheduled` [Date, DateTime or string, default now]: date or datetime when the transfer will be processed. May be pushed to next business day if necessary. ex: ~U[2020-03-26 19:32:35.418698Z]
+    - `:tags` [list of strings]: list of strings for reference when searching for transfers. ex: ["employees", "monthly"]
 
   Attributes (return-only):
     - `:id` [string, default nil]: unique id returned when Transfer is created. ex: "5656565656565656"
@@ -43,6 +45,8 @@ defmodule StarkBank.Transfer do
     :bank_code,
     :branch_code,
     :account_number,
+    :account_type,
+    :external_id,
     :scheduled,
     :transaction_ids,
     :fee,
@@ -242,6 +246,8 @@ defmodule StarkBank.Transfer do
       bank_code: json[:bank_code],
       branch_code: json[:branch_code],
       account_number: json[:account_number],
+      account_type: json[:account_type],
+      external_id: json[:external_id],
       scheduled: json[:scheduled] |> Check.datetime(),
       transaction_ids: json[:transaction_ids],
       fee: json[:fee],
diff --git a/lib/workspace/workspace.ex b/lib/workspace/workspace.ex
index 8d3076b..f11c992 100644
--- a/lib/workspace/workspace.ex
+++ b/lib/workspace/workspace.ex
@@ -20,7 +20,7 @@ defmodule StarkBank.Workspace do
     - `:name` [string]: Full name that identifies the Workspace. This name will appear when people access the Workspace on our platform, for example. Ex: "Stark Bank Workspace"
 
   ## Attributes (return-only):
-    - `:id` [string, default None]: unique id returned when the workspace is created. ex: "5656565656565656"
+    - `:id` [string, default nil]: unique id returned when the workspace is created. ex: "5656565656565656"
   """
   @enforce_keys [
     :username,
diff --git a/test/transfer_test.exs b/test/transfer_test.exs
index c02d67e..0bcb6b0 100644
--- a/test/transfer_test.exs
+++ b/test/transfer_test.exs
@@ -155,7 +155,9 @@ defmodule StarkBankTest.Transfer do
         :crypto.rand_uniform(0, 99999)
         |> to_string
         |> String.pad_leading(5, "0")
-        |> (fn s -> s <> "-#{:crypto.rand_uniform(0, 9)}" end).()
+        |> (fn s -> s <> "-#{:crypto.rand_uniform(0, 9)}" end).(),
+      account_type: ["checking", "savings", "salary"] |> Enum.random(),
+      external_id: "elixir-#{:crypto.rand_uniform(0, 9999999999)}"
     }
   end
 end