diff --git a/validate_docbr/BaseDoc.py b/validate_docbr/BaseDoc.py
index 58e4ec4..bd437eb 100644
--- a/validate_docbr/BaseDoc.py
+++ b/validate_docbr/BaseDoc.py
@@ -45,3 +45,15 @@ def mask(self, doc: str = '') -> str:
     def _only_digits(self, doc: str = '') -> str:
         """Remove os outros caracteres que não sejam dígitos."""
         return "".join([x for x in doc if x.isdigit()])
+
+    def _validate_input(self, input: str, valid_characters: List = None) -> bool:
+        """Validar input.
+        Caso ele possua apenas dígitos e caracteres válidos, retorna True.
+        Caso possua algum caractere que não seja dígito ou caractere válido, retorna False."""
+        if valid_characters is None:
+            valid_characters = ['.', '-', '/', ' ']
+
+        set_non_digit_characters = set([x for x in input if not x.isdigit()])
+        set_valid_characters = set(valid_characters)
+
+        return not (len(set_non_digit_characters.difference(set_valid_characters)) > 0)
diff --git a/validate_docbr/CNH.py b/validate_docbr/CNH.py
index fe500a6..39b23b0 100644
--- a/validate_docbr/CNH.py
+++ b/validate_docbr/CNH.py
@@ -11,6 +11,9 @@ def __init__(self):
 
     def validate(self, doc: str = '') -> bool:
         """Validar CNH."""
+        if not self._validate_input(doc, [' ']):
+            return False
+
         doc = self._only_digits(doc)
 
         if len(doc) != 11 or self._is_repeated_digits(doc):
diff --git a/validate_docbr/CNPJ.py b/validate_docbr/CNPJ.py
index 033856b..1bac731 100644
--- a/validate_docbr/CNPJ.py
+++ b/validate_docbr/CNPJ.py
@@ -13,6 +13,9 @@ def __init__(self):
 
     def validate(self, doc: str = '') -> bool:
         """Validar CNPJ."""
+        if not self._validate_input(doc, ['.', '/', '-']):
+            return False
+
         doc = self._only_digits(doc)
 
         if len(doc) != 14:
diff --git a/validate_docbr/CNS.py b/validate_docbr/CNS.py
index 19080c8..6809867 100644
--- a/validate_docbr/CNS.py
+++ b/validate_docbr/CNS.py
@@ -11,6 +11,9 @@ def __init__(self):
 
     def validate(self, doc: str = '') -> bool:
         """Validar CNS."""
+        if not self._validate_input(doc, [' ']):
+            return False
+
         doc = list(self._only_digits(doc))
 
         if len(doc) != 15 or int(doc[0]) not in self.first_digit:
diff --git a/validate_docbr/CPF.py b/validate_docbr/CPF.py
index 7bfdd42..9ce8e22 100644
--- a/validate_docbr/CPF.py
+++ b/validate_docbr/CPF.py
@@ -12,6 +12,9 @@ def __init__(self, repeated_digits: bool = False):
 
     def validate(self, doc: str = '') -> bool:
         """Validar CPF."""
+        if not self._validate_input(doc, ['.', '-']):
+            return False
+
         doc = list(self._only_digits(doc))
 
         if len(doc) != 11:
@@ -20,7 +23,7 @@ def validate(self, doc: str = '') -> bool:
         if not self.repeated_digits and self._check_repeated_digits(doc):
             return False
 
-        return self._generate_first_digit(doc) == doc[9]\
+        return self._generate_first_digit(doc) == doc[9] \
                and self._generate_second_digit(doc) == doc[10]
 
     def generate(self, mask: bool = False) -> str:
@@ -59,7 +62,7 @@ def _generate_second_digit(self, doc: list) -> str:
         sum = 0
 
         for i in range(11, 1, -1):
-            sum += int(doc[11-i]) * i
+            sum += int(doc[11 - i]) * i
 
         sum = (sum * 10) % 11
 
diff --git a/validate_docbr/PIS.py b/validate_docbr/PIS.py
index ea25658..d896ba1 100644
--- a/validate_docbr/PIS.py
+++ b/validate_docbr/PIS.py
@@ -11,6 +11,9 @@ def __init__(self):
 
     def validate(self, doc: str = '') -> bool:
         """Validar PIS/NIS/PASEP/NIT."""
+        if not self._validate_input(doc, ['.', '-']):
+            return False
+
         doc = self._only_digits(doc)
 
         if len(doc) != 11 or self._is_repeated_digits(doc):
diff --git a/validate_docbr/TituloEleitoral.py b/validate_docbr/TituloEleitoral.py
index 4d9ac82..f7b26c4 100644
--- a/validate_docbr/TituloEleitoral.py
+++ b/validate_docbr/TituloEleitoral.py
@@ -15,6 +15,9 @@ def __init__(self):
 
     def validate(self, doc: str = '') -> bool:
         """Método para validar o título eleitoral."""
+        if not self._validate_input(doc, [' ']):
+            return False
+
         doc_digits = list(map(int, self._only_digits(doc=doc)))
 
         if len(doc_digits) != 12: