Fix: add _approx_equal_price_rounding to allow price in accepable range

cgt_calc/main.py

@@ -31,6 +31,7 @@
 from .model import (
     ActionType,
     BrokerTransaction,
+    CalcuationType,
     CalculationEntry,
     CalculationLog,
     CapitalGainsReport,
@@ -57,6 +58,52 @@ def get_amount_or_fail(transaction: BrokerTransaction) -> Decimal:
     return amount
 
 
+# Amount difference can be caused by rounding errors in the price.
+# Schwab rounds down the price to 4 decimal places
+#  so that the error in amount can be more than $0.01.
+# Fox example:
+# 500 shares of FOO sold at $100.00016 with $1.23 fees.
+# "01/01/2024,"Sell","FOO","FOO","500","$100.0001","$1.23","$49,998.85"
+# calculated_amount = 500 * 100.0001 - 1.23 = 49998.82
+# amount_on_record = 49998.85 vs calculated_amount = 49998.82
+def _approx_equal_price_rounding(
+    amount_on_record: Decimal,
+    quantity_on_record: Decimal,
+    price_on_record: Decimal,
+    fees_on_record: Decimal,
+    calcuationType: CalcuationType,
+) -> bool:
+    calculated_amount = Decimal(0)
+    calculated_price = Decimal(0)
+    if calcuationType is CalcuationType.ACQUISITION:
+        calculated_amount = Decimal(-1) * (
+            quantity_on_record * price_on_record + fees_on_record
+        )
+        calculated_price = (
+            Decimal(-1) * amount_on_record - fees_on_record
+        ) / quantity_on_record
+    elif calcuationType is CalcuationType.DISPOSAL:
+        calculated_amount = quantity_on_record * price_on_record - fees_on_record
+        calculated_price = (amount_on_record + fees_on_record) / quantity_on_record
+    in_acceptable_range = abs(calculated_price - price_on_record) < Decimal("0.0001")
+    LOGGER.debug(
+        "Price calculated_price %.6f vs price_on_record %s in %s",
+        calculated_price,
+        price_on_record,
+        "acceptable range" if in_acceptable_range else "error",
+    )
+    if in_acceptable_range:
+        return True
+    accptable_amount = _approx_equal(amount_on_record, calculated_amount)
+    LOGGER.debug(
+        "Amount amount_on_record %.6f vs calculated_amount %s in %s",
+        amount_on_record,
+        calculated_amount,
+        "acceptable range" if accptable_amount else "error",
+    )
+    return accptable_amount
+
+
 # It is not clear how Schwab or other brokers round the dollar value,
 # so assume the values are equal if they are within $0.01.
 def _approx_equal(val_a: Decimal, val_b: Decimal) -> bool:
@@ -131,7 +178,13 @@ def add_acquisition(
 
             amount = get_amount_or_fail(transaction)
             calculated_amount = quantity * price + transaction.fees
-            if not _approx_equal(amount, -calculated_amount):
+            if not _approx_equal_price_rounding(
+                amount,
+                quantity,
+                price,
+                transaction.fees,
+                CalcuationType.ACQUISITION,
+            ):
                 raise CalculatedAmountDiscrepancyError(transaction, -calculated_amount)
             amount = -amount
 
@@ -265,7 +318,13 @@ def add_disposal(
         if price is None:
             raise PriceMissingError(transaction)
         calculated_amount = quantity * price - transaction.fees
-        if not _approx_equal(amount, calculated_amount):
+        if not _approx_equal_price_rounding(
+            amount,
+            quantity,
+            price,
+            transaction.fees,
+            CalcuationType.DISPOSAL,
+        ):
             raise CalculatedAmountDiscrepancyError(transaction, calculated_amount)
         add_to_list(
             self.disposal_list,

cgt_calc/model.py

@@ -67,6 +67,13 @@ class ActionType(Enum):
     CASH_MERGER = 16
 
 
+class CalcuationType(Enum):
+    """Calculation type enumeration."""
+
+    ACQUISITION = 1
+    DISPOSAL = 2
+
+
 @dataclass
 class BrokerTransaction:
     """Broken transaction data."""

tests/test_data/schwab/expected_output.txt

@@ -0,0 +1,29 @@
+WARNING: No schwab award file provided
+INFO: No schwab Equity Award JSON file provided
+INFO: No trading212 folder provided
+INFO: No mssb folder provided
+INFO: No sharesight file provided
+INFO: No raw file provided
+First pass completed
+Final portfolio:
+Final balance:
+  Charles Schwab: 1019826.86 (USD)
+Dividends: £0.00
+Dividend taxes: £0.00
+Interest: £0.00
+Disposal proceeds: £248079.51
+
+
+Second pass completed
+Portfolio at the end of 2023/2024 tax year:
+For tax year 2023/2024:
+Number of disposals: 3
+Disposal proceeds: £248079.51
+Allowable costs: £232737.33
+Capital gain: £15342.18
+Capital loss: £0.00
+Total capital gain: £15342.18
+Taxable capital gain: £9342.18
+
+Generate calculations report
+All done!

tests/test_data/schwab/schwab_transactions-2023.csv

@@ -0,0 +1,8 @@
+"Date","Action","Symbol","Description","Quantity","Price","Fees & Comm","Amount"
+"03/01/2022","MoneyLink Transfer","","Tfr BANK","","","","$1000000.00"
+"10/09/2023","Buy","BAR","BAR CORP ROUNDING CASE","300","$135.0075","$1.34","-$40503.61"
+"10/24/2023","Sell","BAR","BAR CORP","300","$140.35","$1.34","$42103.66"
+"12/01/2023","Buy","FOO","FOO CORP","500","$90.1234","","-$45061.70"
+"01/08/2024","Sell","FOO","FOO CORP ROUNDING CASE","500","$100.0001","$1.23","$49998.85"
+"02/06/2024","Buy","QUX","QUX CORP ROUNDING CASE","1300","$160.1275","$1.12","-$208166.93"
+"02/26/2024","Sell","QUX","QUX CORP ROUNDING CASE","1300","$170.3521","$1.2","$221456.59"

tests/test_schwab_2023.py

@@ -0,0 +1,29 @@
+"""Test Schwab."""
+
+from pathlib import Path
+import subprocess
+import sys
+
+
+def test_run_with_schwab_example_files() -> None:
+    """Runs the script and verifies it doesn't fail."""
+    cmd = [
+        sys.executable,
+        "-m",
+        "cgt_calc.main",
+        "--year",
+        "2023",
+        "--schwab",
+        "tests/test_data/schwab/schwab_transactions-2023.csv",
+        "--no-pdflatex",
+    ]
+    result = subprocess.run(cmd, check=True, capture_output=True)
+    assert result.stderr == b"", "Run with example files generated errors"
+    expected_file = Path("tests") / "test_data" / "schwab" / "expected_output.txt"
+    expected = expected_file.read_text()
+    cmd_str = " ".join([param if param else "''" for param in cmd])
+    assert result.stdout.decode("utf-8") == expected, (
+        "Run with example files generated unexpected outputs, "
+        "if you added new features update the test with:\n"
+        f"{cmd_str} > {expected_file}"
+    )