diff --git a/src/pymorize/cmorizer.py b/src/pymorize/cmorizer.py
index 71a4607..67b5ff0 100644
--- a/src/pymorize/cmorizer.py
+++ b/src/pymorize/cmorizer.py
@@ -1,6 +1,7 @@
 from pathlib import Path
 
 import dask
+import pandas as pd
 import questionary
 import yaml
 from dask.distributed import Client
@@ -13,9 +14,11 @@
 
 from .data_request import (DataRequest, DataRequestTable, DataRequestVariable,
                            IgnoreTableFiles)
+from .filecache import fc
 from .logging import logger
 from .pipeline import Pipeline
 from .rule import Rule
+from .timeaverage import _frequency_from_approx_interval
 from .utils import wait_for_workers
 from .validate import PIPELINES_VALIDATOR, RULES_VALIDATOR
 
@@ -214,8 +217,46 @@ def _post_init_inherit_rules(self):
 
     def _post_init_checks(self):
         # Sanity Checks:
-        self._check_rules_for_table()
-        self._check_rules_for_output_dir()
+        # :PS: @PG the following functions are not defined yet
+        # self._check_rules_for_table()
+        # self._check_rules_for_output_dir()
+        self._check_is_subperiod()
+
+    def _check_is_subperiod(self):
+        logger.info("checking frequency in netcdf file and in table...")
+        try:
+            rule = self.rules[0]
+        except IndexError:
+            logger.info("No rules found to for checking frequency. ..skipping..")
+            return
+        table_freq = _frequency_from_approx_interval(
+            rule.data_request_variable.table.approx_interval
+        )
+        # is_subperiod from pandas does not support YE or ME notation
+        table_freq = table_freq.rstrip("E")
+        first_filenames = []
+        for input_collection in rule.inputs:
+            try:
+                first_filenames.append(input_collection.files[0])
+            except IndexError:
+                logger.info("No input files found. ..skipping..")
+                return
+        if len(first_filenames) == 1:
+            filename = first_filenames[0]
+            data_freq = fc.get(filename).freq
+        else:  # Multi-variable Rule, handle differently
+            data_freqs = set([fc.get(filename).freq for filename in first_filenames])
+            if len(data_freqs) != 1:
+                raise ValueError(
+                    f"You have a compound variable and have multiple internal frequencies! This is not allowed: {data_freqs}"
+                )
+            data_freq = data_freqs[0]
+        is_subperiod = pd.tseries.frequencies.is_subperiod(data_freq, table_freq)
+        if not is_subperiod:
+            raise ValueError(
+                f"Frequency in source file {data_freq} is not a subperiod of frequency in table {table_freq}."
+            )
+        logger.info(f"Frequency of data {data_freq}. Frequency in tables {table_freq}")
 
     @classmethod
     def from_dict(cls, data):
@@ -244,6 +285,7 @@ def from_dict(cls, data):
         instance._post_init_populate_rules_with_tables()
         instance._post_init_create_data_request()
         instance._post_init_data_request_variables()
+        instance._post_init_checks()
         return instance
 
     def add_rule(self, rule):