diff --git a/lib/iban_ex/commons/commons.ex b/lib/iban_ex/commons/commons.ex
index 713e9cb..243346f 100644
--- a/lib/iban_ex/commons/commons.ex
+++ b/lib/iban_ex/commons/commons.ex
@@ -1,4 +1,6 @@
 defmodule IbanEx.Commons do
+  @moduledoc false
+
   @spec normalize(binary()) :: binary()
   def normalize(string) do
     string
diff --git a/lib/iban_ex/country.ex b/lib/iban_ex/country.ex
index ab2d8ce..2a83641 100644
--- a/lib/iban_ex/country.ex
+++ b/lib/iban_ex/country.ex
@@ -1,4 +1,6 @@
 defmodule IbanEx.Country do
+  @moduledoc false
+
   import IbanEx.Commons, only: [normalize: 1]
 
   @type country_code() :: <<_::16>> | atom()
diff --git a/lib/iban_ex/deserialize.ex b/lib/iban_ex/deserialize.ex
index 38b4e70..9079917 100644
--- a/lib/iban_ex/deserialize.ex
+++ b/lib/iban_ex/deserialize.ex
@@ -7,8 +7,8 @@ end
 defimpl IbanEx.Deserialize, for: [BitString, String] do
   alias IbanEx.{Parser, Error}
   @type iban_or_error() :: IbanEx.Iban.t() | {:error, atom()}
+  @spec to_iban(binary()) :: iban_or_error()
   @spec to_iban(String.t()) :: iban_or_error()
-  @spec to_iban(binary()) :: IbanEx.Iban.t()
   def to_iban(string) do
     case Parser.parse(string) do
       {:ok, iban} -> iban
diff --git a/lib/iban_ex/error.ex b/lib/iban_ex/error.ex
index 7ff22d9..9012d45 100644
--- a/lib/iban_ex/error.ex
+++ b/lib/iban_ex/error.ex
@@ -1,7 +1,5 @@
 defmodule IbanEx.Error do
-  @moduledoc """
-
-  """
+  @moduledoc false
 
   @type error() ::
           :unsupported_country_code
diff --git a/lib/iban_ex/formatter.ex b/lib/iban_ex/formatter.ex
index cdb7421..9c4b7aa 100644
--- a/lib/iban_ex/formatter.ex
+++ b/lib/iban_ex/formatter.ex
@@ -1,4 +1,6 @@
 defmodule IbanEx.Formatter do
+  @moduledoc false
+
   alias IbanEx.Country
   import IbanEx.Commons, only: [normalize: 1]
 
@@ -28,7 +30,7 @@ defmodule IbanEx.Formatter do
 
   def format(iban, :pretty) do
     country_module = Country.country_module(iban.country_code)
-    country_module.to_s(iban)
+    country_module.to_string(iban)
   end
 
   def format(iban, :splitted) do
diff --git a/lib/iban_ex/iban.ex b/lib/iban_ex/iban.ex
index 0443ca5..7a62e53 100644
--- a/lib/iban_ex/iban.ex
+++ b/lib/iban_ex/iban.ex
@@ -1,4 +1,6 @@
 defmodule IbanEx.Iban do
+  @moduledoc false
+
   alias IbanEx.Formatter
   alias IbanEx.{Serialize}
 
diff --git a/lib/iban_ex/parser.ex b/lib/iban_ex/parser.ex
index b2391cb..cc89647 100644
--- a/lib/iban_ex/parser.ex
+++ b/lib/iban_ex/parser.ex
@@ -1,4 +1,6 @@
 defmodule IbanEx.Parser do
+  @moduledoc false
+
   alias IbanEx.{Country, Iban, Validator}
   import IbanEx.Commons, only: [normalize_and_slice: 2]
 
@@ -9,20 +11,27 @@ defmodule IbanEx.Parser do
 
   @spec parse({:ok, String.t()} | String.t()) :: iban_or_error()
   def parse({:ok, iban_string}), do: parse(iban_string)
+
   def parse(iban_string) do
-    with {:ok, valid_iban} <- Validator.validate(iban_string) do
-      iban_map = %{
-        country_code: country_code(valid_iban),
-        check_digits: check_digits(valid_iban),
-      }
+    case Validator.validate(iban_string) do
+      {:ok, valid_iban} ->
+        iban_map = %{
+          country_code: country_code(valid_iban),
+          check_digits: check_digits(valid_iban)
+        }
 
-      regex = Country.country_module(iban_map.country_code).rule()
-      bban = bban(iban_string)
-      bban_map = for {key, val} <- Regex.named_captures(regex, bban), into: %{}, do: {String.to_atom(key), val}
+        regex = Country.country_module(iban_map.country_code).rule()
+        bban = bban(iban_string)
 
-      {:ok, struct(Iban, Map.merge(iban_map, bban_map))}
-    else
-      {:error, error_type} -> {:error, error_type}
+        bban_map =
+          for {key, val} <- Regex.named_captures(regex, bban),
+              into: %{},
+              do: {String.to_atom(key), val}
+
+        {:ok, struct(Iban, Map.merge(iban_map, bban_map))}
+
+      {:error, error_type} ->
+        {:error, error_type}
     end
   end
 
diff --git a/lib/iban_ex/serialize.ex b/lib/iban_ex/serialize.ex
index 0a5e0fc..c7445fb 100644
--- a/lib/iban_ex/serialize.ex
+++ b/lib/iban_ex/serialize.ex
@@ -1,4 +1,6 @@
 defmodule IbanEx.Serialize do
+  @moduledoc false
+
   alias IbanEx.{Iban, Formatter}
 
   @spec to_string(Iban.t()) :: String.t()
diff --git a/lib/iban_ex/validator/validator.ex b/lib/iban_ex/validator/validator.ex
index ec7558a..e4d9caa 100644
--- a/lib/iban_ex/validator/validator.ex
+++ b/lib/iban_ex/validator/validator.ex
@@ -1,9 +1,11 @@
 defmodule IbanEx.Validator do
+  @moduledoc false
+
   alias IbanEx.{Country, Parser}
   alias IbanEx.Validator.Replacements
   import IbanEx.Commons, only: [normalize: 1]
 
-  @spec validate(String.t()) :: {:ok, String.t()} | {:error}
+  @spec validate(String.t()) :: {:ok, String.t()} | {:error, Atom.t()}
   def validate(iban) do
     cond do
       iban_violates_format?(iban) ->