Add support for annual exchange rates

Download annual exchange rates from HMRC and option to use them instead of monthly.

Had to use library to map country name to currencyCode as different years have completely different formats of the file

cgt_calc/args_parser.py

@@ -124,6 +124,13 @@ def create_parser() -> argparse.ArgumentParser:
             " if you were to sell your holdings, under the standard 104 rule."
         ),
     )
+    parser.add_argument(
+        "--exchange-rate-type",
+        type=str,
+        choices=["monthly", "annual"],
+        default="monthly",
+        help="Type of HRMC exchange rate to use (default: %(default)s)",
+    )
     parser.add_argument(
         "--verbose",
         action="store_true",
@@ -140,4 +147,5 @@ def create_parser() -> argparse.ArgumentParser:
         action="store_true",
         help=argparse.SUPPRESS,
     )
+
     return parser

cgt_calc/currency_converter.py

@@ -5,15 +5,18 @@
 from collections import defaultdict
 import csv
 import datetime
-from decimal import Decimal
+from decimal import Decimal, InvalidOperation
 from pathlib import Path
 from typing import TYPE_CHECKING, Final
 
 from defusedxml import ElementTree as ET
 import requests
+import pycountry
 
 from .dates import is_date
 from .exceptions import ExchangeRateMissingError, ParsingError
+from enum import Enum
+from .model import ExchangeRateType
 
 if TYPE_CHECKING:
     from .model import BrokerTransaction
@@ -29,6 +32,7 @@ def __init__(
         self,
         exchange_rates_file: str | None = None,
         initial_data: dict[datetime.date, dict[str, Decimal]] | None = None,
+        rate_type: ExchangeRateType = ExchangeRateType.MONTHLY,
     ):
         """Load data from exchange_rates_file and optionally from initial_data."""
         self.exchange_rates_file = exchange_rates_file
@@ -38,6 +42,8 @@ def __init__(
             **(initial_data or {}),
         }
         self.session = requests.Session()
+        self.rate_type = rate_type
+        print(f"Using {self.rate_type.value} exchange rates from HMRC")
 
     @staticmethod
     def _read_exchange_rates_file(
@@ -79,24 +85,37 @@ def _write_exchange_rates_file(
             writer = csv.writer(fout)
             writer.writerows([EXCHANGE_RATES_HEADER, *data_rows])
 
+
     def _query_hmrc_api(self, date: datetime.date) -> None:
-        # Pre 2021 we need to use the old HMRC endpoint
-        if date.year < NEW_ENDPOINT_FROM_YEAR:
-            month_str = date.strftime("%m%y")
-            url = (
-                "http://www.hmrc.gov.uk/softwaredevelopers/rates/"
-                f"exrates-monthly-{month_str}.xml"
-            )
-        else:
-            month_str = date.strftime("%Y-%m")
+        """Query HMRC API for exchange rates."""
+
+        if self.rate_type == ExchangeRateType.MONTHLY:
+            # Pre 2021 we need to use the old HMRC endpoint
+            if date.year < NEW_ENDPOINT_FROM_YEAR:
+                month_str = date.strftime("%m%y")
+                url = (
+                    "http://www.hmrc.gov.uk/softwaredevelopers/rates/"
+                    f"exrates-monthly-{month_str}.xml"
+                )
+            else:
+                month_str = date.strftime("%Y-%m")
+                url = (
+                    "https://www.trade-tariff.service.gov.uk/api/v2/"
+                    f"exchange_rates/files/monthly_xml_{month_str}.xml"
+                )
+        else:  # ExchangeRateType.ANNUAL
+            year_str = date.strftime("%Y")
+            month_str = "12"  # Annual rates are published in December
             url = (
                 "https://www.trade-tariff.service.gov.uk/api/v2/"
-                f"exchange_rates/files/monthly_xml_{month_str}.xml"
+                f"exchange_rates/files/average_csv_{year_str}-{month_str}.csv"
             )
+
         try:
             response = self.session.get(url, timeout=10)
         except Exception as err:
-            msg = f"Error while fetching HMRC exchange rates for the month {month_str} "
+            period = "month" if self.rate_type == ExchangeRateType.MONTHLY else "year"
+            msg = f"Error while fetching HMRC exchange rates for the {period} {date.strftime('%Y-%m')} "
             msg += f"from the following url: {url}.\n"
             msg += "Either try again or if you're sure about the rates you can "
             msg += f"add them manually in {self.exchange_rates_file}.\n"
@@ -108,18 +127,52 @@ def _query_hmrc_api(self, date: datetime.date) -> None:
                 url, f"HMRC API returned a {response.status_code} response"
             )
 
-        tree = ET.fromstring(response.text)
-        rates = {
-            str(getattr(row.find("currencyCode"), "text", None)).upper(): Decimal(
-                str(getattr(row.find("rateNew"), "text", None))
-            )
-            for row in tree
-        }
+        if self.rate_type == ExchangeRateType.MONTHLY:
+            tree = ET.fromstring(response.text)
+            rates = {
+                str(getattr(row.find("currencyCode"), "text", None)).upper(): Decimal(
+                    str(getattr(row.find("rateNew"), "text", None))
+                )
+                for row in tree
+            }
+        else:  # ExchangeRateType.ANNUAL
+            csv_data = csv.DictReader(response.text.splitlines())
+            rates = self.parse_annual_rates_csv(csv_data)
+
         if None in rates or None in rates.values():
             raise ParsingError(url, "HMRC API produced invalid/unknown data")
         self.cache[date] = rates
         self._write_exchange_rates_file(self.exchange_rates_file, self.cache)
 
+    def parse_annual_rates_csv(self, csv_data):
+        """Parse annual rates CSV data from HMRC."""
+        rates = {}
+        for row in csv_data:
+            try:
+                if 'Currency Code' in row:
+                    # Use currencyCode if available
+                    currency = row['Currency Code'].strip().upper()
+                    rate = Decimal(row['Currency Units per £1'])
+                    rates[currency] = rate
+                else:
+                    # Fall back to checking country name
+                    first_col = next(iter(row))
+                    country_name = row[first_col].strip()
+                    rate = Decimal(row['Currency Units per pound'])
+
+                    # Try to find country by name or code
+                    country = (
+                        pycountry.countries.get(name=country_name) or 
+                        pycountry.countries.get(alpha_3=country_name)
+                    )
+                    if country:
+                        currency = pycountry.currencies.get(numeric=country.numeric)
+                        if currency:
+                            rates[currency.alpha_3] = rate
+            except (KeyError, InvalidOperation, AttributeError):
+                continue
+        return rates
+
     def currency_to_gbp_rate(self, currency: str, date: datetime.date) -> Decimal:
         """Get GBP/currency rate at given date."""
         assert is_date(date)

cgt_calc/main.py

@@ -40,6 +40,7 @@
     Position,
     RuleType,
     SpinOff,
+    ExchangeRateType,
 )
 from .parsers import read_broker_transactions, read_initial_prices
 from .spin_off_handler import SpinOffHandler
@@ -836,7 +837,10 @@ def main() -> int:
         args.sharesight,
         args.raw,
     )
-    converter = CurrencyConverter(args.exchange_rates_file)
+    converter = CurrencyConverter(
+        args.exchange_rates_file,
+        rate_type=ExchangeRateType(args.exchange_rate_type),
+    )
     initial_prices = InitialPrices(read_initial_prices(args.initial_prices))
     price_fetcher = CurrentPriceFetcher(converter)
     spin_off_handler = SpinOffHandler(args.spin_offs_file)

cgt_calc/model.py

@@ -275,3 +275,9 @@ def __str__(self) -> str:
                     " and factor in their prices.\n"
                 )
         return out
+
+
+class ExchangeRateType(Enum):
+    """Type of exchange rate to use from HMRC."""
+    MONTHLY = "monthly"
+    ANNUAL = "annual"