Test for splits

cgt_calc/main.py

@@ -42,7 +42,7 @@
 )
 from .parsers import read_broker_transactions, read_initial_prices
 from .spin_off_handler import SpinOffHandler
-from .transaction_log import add_to_list, has_key
+from .transaction_log import add_to_list, has_key, multiply_entries
 from .util import round_decimal
 
 LOGGER = logging.getLogger(__name__)
@@ -123,7 +123,16 @@ def add_acquisition(
             price, amount = self.handle_spin_off(transaction)
         elif transaction.action is ActionType.STOCK_SPLIT:
             price = Decimal(0)
-            amount = Decimal(0)
+            original = self.portfolio[symbol].quantity
+            multiple = Decimal((original + quantity) / original)
+            # Retroactively alter the acquisition / disposal list, instead of
+            # adding the split as a separate acquisition event.
+            multiply_entries(
+                self.acquisition_list, symbol, multiple, transaction.date)
+            multiply_entries(
+                self.disposal_list, symbol, multiple, transaction.date)
+            self.portfolio[symbol] += Position(quantity, Decimal(0))
+            return
         else:
             if price is None:
                 raise PriceMissingError(transaction)

cgt_calc/transaction_log.py

@@ -31,3 +31,15 @@ def add_to_list(
         amount=amount,
         fees=fees,
     )
+
+def multiply_entries(
+    current_list: HmrcTransactionLog,
+    symbol: str,
+    multiple: Decimal,
+    multiply_date: datetime.date | None = None
+) -> None:
+    for date, entries in current_list.items():
+        if multiply_date is not None:
+            assert multiply_date >= date
+        entries[symbol].quantity *= multiple
+

tests/test_data/calc_test_data.py

@@ -89,6 +89,26 @@ def transaction(
     )
 
 
+def split_transaction(
+    date: datetime.date,
+    symbol: str,
+    quantity: float,
+) -> BrokerTransaction:
+    """Create sell transaction."""
+    return BrokerTransaction(
+        date,
+        ActionType.STOCK_SPLIT,
+        symbol,
+        f"Split of {symbol}",
+        round_decimal(Decimal(quantity), 6),
+        price=Decimal(0),
+        fees=Decimal(0),
+        amount=Decimal(0),
+        currency="USD",
+        broker="Testing",
+    )
+
+
 calc_basic_data = [
     pytest.param(
         2020,  # tax year
@@ -992,4 +1012,87 @@ def transaction(
         },
         id="sell_on_30/6_is_split_into_104+same_day+b&d",
     ),
+    pytest.param(
+        2023,  # tax year
+        [
+            transfer_transaction(datetime.date(day=1, month=5, year=2020), 100),
+            buy_transaction(
+                date=datetime.date(day=2, month=5, year=2023),
+                symbol="FOO",
+                quantity=12,
+                price=5,
+                amount=-60,
+                fees=0,
+            ),
+            sell_transaction(
+                date=datetime.date(day=10, month=5, year=2023),
+                symbol="FOO",
+                quantity=2,
+                price=6,
+                amount=12,  # 2.00 gain
+                fees=0,
+            ),
+            split_transaction(
+                date=datetime.date(day=15, month=5, year=2023),
+                symbol="FOO",
+                quantity=10,  # 2x split
+            ),
+            sell_transaction(
+                date=datetime.date(day=10, month=6, year=2023),
+                symbol="FOO",
+                quantity=2,
+                price=5,
+                amount=10,  # 5.00 gain
+                fees=0,
+            ),
+        ],
+        7.00,  # Expected capital gain/loss
+        None,  # Expected unrealized gains
+        None,  # GBP/USD prices
+        None,  # Current prices
+        {
+            datetime.date(day=2, month=5, year=2023): {
+                "buy$FOO": [
+                    CalculationEntry(
+                        RuleType.SECTION_104,
+                        quantity=Decimal(24),
+                        amount=Decimal(-60),
+                        allowable_cost=Decimal(60),
+                        new_quantity=Decimal(24),
+                        fees=Decimal(0),
+                        new_pool_cost=Decimal(60),
+                    ),
+                ],
+            },
+            datetime.date(day=10, month=5, year=2023): {
+                "sell$FOO": [
+                    CalculationEntry(
+                        RuleType.SECTION_104,
+                        quantity=Decimal(4),
+                        amount=Decimal(12),
+                        gain=Decimal(2),
+                        allowable_cost=Decimal(10),
+                        fees=Decimal(0),
+                        new_quantity=Decimal(20),
+                        new_pool_cost=Decimal(50),
+                    ),
+                ],
+            },
+            datetime.date(day=10, month=6, year=2023): {
+                "sell$FOO": [
+                    CalculationEntry(
+                        RuleType.SECTION_104,
+                        quantity=Decimal(2),
+                        amount=Decimal(10),
+                        gain=Decimal(5),
+                        fees=Decimal(0),
+                        allowable_cost=Decimal(5),
+                        new_quantity=Decimal(18),
+                        new_pool_cost=Decimal(45),
+                    ),
+                ],
+            },
+        },
+        id="split",
+    ),
 ]