diff --git a/rrn.py b/rrn.py
index c332644..73fe7d5 100644
--- a/rrn.py
+++ b/rrn.py
@@ -1,6 +1,7 @@
 import itertools
 import re
-from datetime import datetime
+from datetime import date, datetime
+from typing import Optional
 
 
 HYPHEN = re.compile('[-–]')
@@ -10,6 +11,8 @@
 MONTH_OF_BIRTH_FORMAT = '%y%m'
 DAY_OF_BIRTH_FORMAT = '%y%m%d'
 
+SEX = 6
+
 LOC = 7, 9
 MAX_LOC = 97
 
@@ -84,5 +87,61 @@ def is_valid_rrn(rrn: str) -> bool:
         return False
 
 
-def is_corresponding_rrn(rrn: str) -> bool:
-    pass
+def _is_birthday_corresponding(rrn: str, birthday: date) -> Optional[bool]:
+    try:
+        return datetime.strptime(
+            rrn[slice(*BIRTH)],
+            DAY_OF_BIRTH_FORMAT
+        ).date() == birthday
+    except (TypeError, ValueError):
+        return None
+
+
+def _is_sex_corresponding(rrn: str, female: bool) -> Optional[bool]:
+    try:
+        return (int(rrn[SEX]) % 2 == 0) == female
+    except IndexError:
+        return None
+
+
+def _is_foreignness_corresponding(rrn: str, foreign: bool) -> Optional[bool]:
+    try:
+        return (5 <= int(rrn[SEX]) <= 8) == foreign
+    except IndexError:
+        return None
+
+
+def is_corresponding_rrn(
+    rrn: str,
+    *,
+    birthday: Optional[date]=None,
+    foreign: Optional[bool]=None,
+    female: Optional[bool]=None
+) -> Optional[bool]:
+    """
+    Check given RRN if it corresponds with given information or not.
+    It returns None if correspondence is undecidable.
+    For example, 6-digit RRN string does not contain any information about sex.
+
+    :param rrn: RRN string
+    :param birthday: expected date of birth
+    :param foreign: expected to be foreigner or not
+    :param female: expected to be female or not
+    :return: correspondence (None if it's undecidable)
+    """
+    try:
+        rrn = HYPHEN.sub('', rrn)
+        assert rrn.isdigit()
+        return (
+            (
+                birthday is None or _is_birthday_corresponding(rrn, birthday)
+            ) and
+            (
+                foreign is None or _is_foreignness_corresponding(rrn, foreign)
+            ) and
+            (
+                female is None or _is_sex_corresponding(rrn, female)
+            )
+        )
+    except (AssertionError, TypeError):
+        return None
diff --git a/tests/test_rrn.py b/tests/test_rrn.py
index 9916460..eb2fa10 100644
--- a/tests/test_rrn.py
+++ b/tests/test_rrn.py
@@ -1,4 +1,5 @@
 import unittest
+from datetime import date
 
 import rrn
 
@@ -42,4 +43,27 @@ def test_is_valid_rrn(self):
             self.assertEqual(expected, rrn.is_valid_rrn(s))
 
     def test_is_corresponding_rrn(self):
-        self.assertEqual(1 + 1, 2)
+        undecided, corresponding, not_corresponding = None, True, False
+        female, male = True, False
+        foreign, domestic = True, False
+
+        for r, (b, s, f), expected in [
+            ('RRN', (None, None, None), undecided),
+            ('940812', (None, None, None), corresponding),
+            ('940812', (None, male, None), undecided),
+            ('940812', (None, None, foreign), undecided),
+            ('940812', (None, female, foreign), undecided),
+            ('8808121', (None, male, domestic), corresponding),
+            ('6008122', (None, None, foreign), not_corresponding),
+            ('7403225', (None, female, None), not_corresponding),
+            ('9408131', (date(1994, 8, 13), None, None), corresponding),
+            ('9408121', (date(1994, 8, 12), None, domestic), corresponding),
+            ('0408127', (date(2004, 8, 12), male, domestic), not_corresponding),
+            ('9408122', (date(1994, 8, 12), female, domestic), corresponding),
+            ('9802145', (date(1998, 2, 14), male, foreign), corresponding),
+            ('9103226', (date(1991, 3, 22), female, foreign), corresponding)
+        ]:
+            self.assertEqual(
+                expected,
+                rrn.is_corresponding_rrn(r, birthday=b, female=s, foreign=f)
+            )