diff --git a/conservancy_beancount/reconcile/statement_reconciler.py b/conservancy_beancount/reconcile/statement_reconciler.py
index 17dc912..f42000c 100644
--- a/conservancy_beancount/reconcile/statement_reconciler.py
+++ b/conservancy_beancount/reconcile/statement_reconciler.py
@@ -295,6 +295,20 @@ def format_multirecord(r1s: List[dict], r2s: List[dict], note: str) -> List[list
     return match_output
 
 
+def _start_of_month(time, offset_months=0):
+    if offset_months > 0:
+        return _start_of_month(time.replace(day=28) + datetime.timedelta(days=4), offset_months - 1)
+    else:
+        return time.replace(day=1)
+
+
+def round_to_month(begin_date, end_date):
+    """Round a beginning and end date to beginning and end of months respectively."""
+    return (
+        _start_of_month(begin_date),
+        _start_of_month(end_date, offset_months=1) - datetime.timedelta(days=1))
+
+
 def sort_records(records: List) -> List:
     return sorted(records, key=lambda x: (x['date'], x['amount']))
 
@@ -596,6 +610,7 @@ def parse_arguments(argv: List[str]) -> argparse.Namespace:
     # parser.add_argument('--report-group-regex')
     parser.add_argument('--show-reconciled-matches', action='store_true')
     parser.add_argument('--non-interactive', action='store_true', help="Don't prompt to write to the books")    # parser.add_argument('--statement-balance', type=parse_decimal_with_separator, required=True, help="A.K.A \"cleared balance\" taken from the end of the period on the PDF statement. Required because CSV statements don't include final or running totals")
+    parser.add_argument('--full-months', action='store_true', help='Match payments over the full month, rather that just between the beginning and end dates of the CSV statement')
     args = parser.parse_args(args=argv)
     return args
 
@@ -676,6 +691,9 @@ def main(arglist: Optional[Sequence[str]] = None,
     begin_date = statement_trans[0]['date']
     end_date = statement_trans[-1]['date']
 
+    if args.full_months:
+        begin_date, end_date = round_to_month(begin_date, end_date)
+
     # Query for the Beancount books data for this above period.
     #
     # There are pros and cons for using Beancount's in-memory entries
diff --git a/tests/test_reconcile.py b/tests/test_reconcile.py
index 292de36..ba6d6ac 100644
--- a/tests/test_reconcile.py
+++ b/tests/test_reconcile.py
@@ -5,6 +5,8 @@ import os
 import tempfile
 import textwrap
 
+import pytest
+
 from conservancy_beancount.reconcile.statement_reconciler import (
     date_proximity,
     format_output,
@@ -15,6 +17,7 @@ from conservancy_beancount.reconcile.statement_reconciler import (
     read_fr_csv,
     remove_duplicate_words,
     remove_payee_junk,
+    round_to_month,
     subset_match,
     totals,
     write_metadata_to_books,
@@ -388,3 +391,20 @@ def test_format_output():
     matches, _, _ = match_statement_and_books(statement, books)
     output = format_output(matches, datetime.date(2022, 1, 1), datetime.date(2022, 2, 1), 'test.csv', True)
     assert '2022-01-01:       10.00 Patreon         / Patreon   / 12345  →  2022-01-01:       10.00 Patreon                              ✓ Matched' in output
+
+
+month_test_data = [
+    ((datetime.date(2022, 1, 2), datetime.date(2022, 1, 30)),
+     (datetime.date(2022, 1, 1), datetime.date(2022, 1, 31))),
+    ((datetime.date(2022, 4, 2), datetime.date(2022, 4, 29)),
+     (datetime.date(2022, 4, 1), datetime.date(2022, 4, 30))),
+    ((datetime.date(2022, 2, 2), datetime.date(2022, 2, 27)),
+     (datetime.date(2022, 2, 1), datetime.date(2022, 2, 28))),
+    ((datetime.date(2024, 2, 2), datetime.date(2024, 2, 27)),
+     (datetime.date(2024, 2, 1), datetime.date(2024, 2, 29))),
+]
+
+
+@pytest.mark.parametrize('input_dates,rounded_dates', month_test_data)
+def test_rounds_to_full_month(input_dates, rounded_dates):
+    assert round_to_month(*input_dates) == rounded_dates