Correct vdb scheduling issue

dcaf/tax/depreciation.py

@@ -150,7 +150,7 @@ def _build_vdb_candidate_schedule(
     period_number = 0
 
     for current_date in dates:
-        if current_date <= placed_in_service:
+        if current_date < placed_in_service:
             continue
         period_number += 1
 
@@ -411,7 +411,8 @@ def vdb_schedule(
     schedule_dates : Sequence[date] | None, optional
         Explicit dates for convention-aware schedule entries. When provided,
         depreciation flows are placed on these dates instead of
-        ``placed_in_service + n * frequency``.
+        ``placed_in_service + n * frequency``. Dates before
+        ``placed_in_service`` are ignored; a matching date is included.
     valuation_rate : float | None, optional
         Annual discount rate used when ``convention`` is
         ``"best-of-half-year-mid-quarter"``.
@@ -470,7 +471,7 @@ def vdb_schedule(
     ...     terminal_catch_up=True,
     ... )
     >>> aligned.entries[0].date
-    datetime.date(2031, 12, 31)
+    datetime.date(2030, 12, 31)
     """
     if isinstance(life, bool) or not isinstance(life, int) or life <= 0:
         raise ValueError("life must be a positive integer")
@@ -508,7 +509,7 @@ def vdb_schedule(
     if convention != "none":
         if normalized_schedule_dates is None:
             delta = time_delta_per_period(frequency)
-            period_count = life + 1 + (1 if terminal_catch_up else 0)
+            period_count = life + (1 if terminal_catch_up else 0)
             generated_dates: list[date] = []
             current_date = placed_in_service
             for _ in range(period_count):

tests/unit/test_depreciation.py

@@ -172,12 +172,28 @@ def test_vdb_schedule_half_year_convention_can_add_terminal_catch_up():
     )
 
     assert stream.count() == 6
-    assert stream.entries[0].date == date(2027, 1, 1)
+    assert stream.entries[0].date == date(2026, 1, 1)
+    assert stream.entries[-1].date == date(2031, 1, 1)
     assert -stream.entries[0].amount == pytest.approx(200.0)
     assert -stream.entries[-1].amount == pytest.approx(54.0)
     assert sum(entry.amount for entry in stream.entries) == pytest.approx(-1000.0)
 
 
+def test_vdb_schedule_half_year_convention_without_catch_up_has_life_entries():
+    """Including the placed-in-service date must not add an extra schedule period."""
+    stream = vdb_schedule(
+        cost_basis=1000.0,
+        salvage_value=0.0,
+        placed_in_service=date(2026, 1, 1),
+        life=5,
+        convention="half-year",
+    )
+
+    assert [entry.date for entry in stream.entries] == [
+        date(year, 1, 1) for year in range(2026, 2031)
+    ]
+
+
 def test_vdb_schedule_mid_quarter_convention_uses_explicit_date_grid():
     """Convention-aware schedules should align entries to the supplied date grid."""
     schedule_dates = (
@@ -248,6 +264,7 @@ def test_vdb_mid_quarter_first_period_by_quarter(placed, expected_first_period):
         schedule_dates=tuple(date(year, 12, 31) for year in range(2029, 2037)),
         terminal_catch_up=True,
     )
+    assert stream.entries[0].date == date(2030, 12, 31)
     assert -stream.entries[0].amount == pytest.approx(expected_first_period)
 
 
@@ -271,7 +288,7 @@ def test_vdb_schedule_best_of_convention_matches_workbook_shape():
     schedule_dates = tuple(date(year, 12, 31) for year in range(2030, 2047))
     # Workbook models the asset entering service at the start of 2031 (Q1), with the
     # first deduction at year-end 2031. Under literal-date quarter semantics that is
-    # the date 2031-01-01 (skips the 2030-12-31 grid point as an exclusive lower bound).
+    # the date 2031-01-01, so the preceding 2030-12-31 grid point is skipped.
     stream = vdb_schedule(
         cost_basis=877824.3662585187,
         salvage_value=0.0,