diff --git a/doc/source/development/contributing.rst b/doc/source/development/contributing.rst
index 3cdf9b83e96f3..97807d3c9e686 100644
--- a/doc/source/development/contributing.rst
+++ b/doc/source/development/contributing.rst
@@ -949,6 +949,15 @@ the expected correct result::
 
         assert_frame_equal(pivoted, expected)
 
+.. note::
+
+   Add the GitHub issue number as a comment to the new tests.
+   For Example - For a test solving issue number 20172, write
+     | def test_apply_categorical_with_nan_values(self, series):
+     |       # GH 20172
+     |       s = pd.Series(series, dtype="category")
+     |       ...
+
 Transitioning to ``pytest``
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~