diff --git a/stdnum/cz/ico.py b/stdnum/cz/ico.py
new file mode 100644
index 00000000..87395588
--- /dev/null
+++ b/stdnum/cz/ico.py
@@ -0,0 +1,92 @@
+# ico.py - functions for handling Czech organisation identifiers
+# coding: utf-8
+#
+# Copyright (C) 2026 Devashish Moghe
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, see <https://www.gnu.org/licenses/>.
+
+"""IČO (Identifikační číslo osoby, Czech organisation identifier).
+
+The IČO (Identifikační číslo osoby, also abbreviated IČ) is an 8-digit
+number (including a trailing check digit) that uniquely identifies a legal
+entity or sole trader registered in the Czech Republic. It is assigned by
+the Czech Statistical Office and is listed in the public business register
+(ARES).
+
+The number is the same as the digits of the legal entity's Czech VAT number
+(DIČ, see stdnum.cz.dic) without the ``CZ`` prefix.
+
+More information:
+
+* https://cs.wikipedia.org/wiki/Identifikační_číslo_osoby
+* https://ares.gov.cz/
+
+>>> validate('00177041')
+'00177041'
+>>> validate('001 77 041')
+'00177041'
+>>> validate('00177042')  # invalid check digit
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+>>> validate('0017704')  # too short
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+>>> validate('0017704X')
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+"""
+
+from __future__ import annotations
+
+from stdnum.exceptions import *
+from stdnum.util import clean, isdigits
+
+
+def compact(number: str) -> str:
+    """Convert the number to the minimal representation. This strips the
+    number of any valid separators and removes surrounding whitespace."""
+    return clean(number, ' /').strip()
+
+
+def calc_check_digit(number: str) -> str:
+    """Calculate the check digit. The number passed should not have the
+    check digit included."""
+    # weighted modulo 11 checksum; this is the same algorithm used for the
+    # 8-digit (legal entity) form of the Czech DIČ, see stdnum.cz.dic
+    check = (11 - sum((8 - i) * int(n) for i, n in enumerate(number))) % 11
+    return str((check or 1) % 10)
+
+
+def validate(number: str) -> str:
+    """Check if the number is a valid IČO. This checks the length,
+    formatting and check digit."""
+    number = compact(number)
+    if not isdigits(number):
+        raise InvalidFormat()
+    if len(number) != 8:
+        raise InvalidLength()
+    if number[-1] != calc_check_digit(number[:-1]):
+        raise InvalidChecksum()
+    return number
+
+
+def is_valid(number: str) -> bool:
+    """Check if the number is a valid IČO."""
+    try:
+        return bool(validate(number))
+    except ValidationError:
+        return False
diff --git a/stdnum/sk/ico.py b/stdnum/sk/ico.py
new file mode 100644
index 00000000..bab59124
--- /dev/null
+++ b/stdnum/sk/ico.py
@@ -0,0 +1,52 @@
+# ico.py - functions for handling Slovak organisation identifiers
+# coding: utf-8
+#
+# Copyright (C) 2026 Devashish Moghe
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, see <https://www.gnu.org/licenses/>.
+
+"""IČO (Identifikačné číslo organizácie, Slovak organisation identifier).
+
+The IČO (Identifikačné číslo organizácie) is an 8-digit number (including a
+trailing check digit) that identifies an organisation or sole trader
+registered in Slovakia. It is listed in the Slovak business register (ORSR)
+and the Register of Legal Entities (RPO).
+
+This number is identical to the Czech counterpart (until 1993 the Czech
+Republic and Slovakia were one country) and uses the same format and check
+digit.
+
+>>> validate('31322832')
+'31322832'
+>>> validate('31 322 832')
+'31322832'
+>>> validate('31322833')  # invalid check digit
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+>>> validate('313228')  # too short
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+"""
+
+# since this number is essentially the same as the Czech counterpart
+# (until 1993 the Czech Republic and Slovakia were one country)
+
+from __future__ import annotations
+
+from stdnum.cz.ico import calc_check_digit, compact, is_valid, validate
+
+
+__all__ = ['compact', 'calc_check_digit', 'validate', 'is_valid']
diff --git a/tests/test_cz_ico.doctest b/tests/test_cz_ico.doctest
new file mode 100644
index 00000000..f772702d
--- /dev/null
+++ b/tests/test_cz_ico.doctest
@@ -0,0 +1,80 @@
+test_cz_ico.doctest - more detailed doctests for the stdnum.cz.ico module
+
+Copyright (C) 2026 Devashish Moghe
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, see <https://www.gnu.org/licenses/>.
+
+
+This file contains more detailed doctests for the stdnum.cz.ico module. It
+tries to validate a number of numbers that have been found online.
+
+>>> from stdnum.cz import ico
+>>> from stdnum.exceptions import *
+
+
+Tests for some corner cases.
+
+>>> ico.validate('00177041')
+'00177041'
+>>> ico.validate('001 77 041')
+'00177041'
+>>> ico.compact('001 77 041')
+'00177041'
+>>> ico.is_valid('00177041')
+True
+>>> ico.is_valid('00177042')
+False
+>>> ico.validate('00177042')
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+>>> ico.validate('123')
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+>>> ico.validate('2616868A')
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+
+
+These have been found online and should all be valid numbers.
+
+>>> numbers = '''
+...
+... 00001350
+... 00006947
+... 00177041
+... 00514152
+... 01377281
+... 24704415
+... 25063677
+... 25672720
+... 26168685
+... 26185610
+... 28195329
+... 27082440
+... 45244782
+... 45272956
+... 45274649
+... 45317054
+... 45357366
+... 47114983
+... 49240901
+... 60193336
+... 70994226
+...
+... '''
+>>> [x for x in numbers.splitlines() if x and not ico.is_valid(x)]
+[]
diff --git a/tests/test_sk_ico.doctest b/tests/test_sk_ico.doctest
new file mode 100644
index 00000000..1469291d
--- /dev/null
+++ b/tests/test_sk_ico.doctest
@@ -0,0 +1,78 @@
+test_sk_ico.doctest - more detailed doctests for the stdnum.sk.ico module
+
+Copyright (C) 2026 Devashish Moghe
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, see <https://www.gnu.org/licenses/>.
+
+
+This file contains more detailed doctests for the stdnum.sk.ico module. It
+tries to validate a number of numbers that have been found online.
+
+>>> from stdnum.sk import ico
+>>> from stdnum.exceptions import *
+
+
+Tests for some corner cases.
+
+>>> ico.validate('31322832')
+'31322832'
+>>> ico.validate('31 322 832')
+'31322832'
+>>> ico.is_valid('31322832')
+True
+>>> ico.is_valid('31322833')
+False
+>>> ico.validate('31322833')
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+>>> ico.validate('313228')
+Traceback (most recent call last):
+    ...
+InvalidLength: ...
+>>> ico.validate('3132283A')
+Traceback (most recent call last):
+    ...
+InvalidFormat: ...
+
+
+These have been found online and should all be valid numbers.
+
+>>> numbers = '''
+...
+... 00151653
+... 00151742
+... 00686930
+... 31320155
+... 31321828
+... 31322832
+... 31333532
+... 31364501
+... 35697270
+... 35743565
+... 35757442
+... 35763469
+... 35790253
+... 35815256
+... 35829052
+... 35848863
+... 35876832
+... 35971894
+... 36199222
+... 36631124
+... 44483767
+...
+... '''
+>>> [x for x in numbers.splitlines() if x and not ico.is_valid(x)]
+[]