Imports name this capability’s declared dependencies, which fune builds next to it in your project; each one links to its page.
import re
from typing import Optional, Tuple
from .fleet_mileage_allowance_data import AMAP_RATES, AMAP_RATES_HISTORY ← this capability’s own data, compiled from data/amap-rates.json into the same file by fune build
from .fleet_mileage_allowance_types import MileageAllowance, MileageVehicle
from .money_add import subtract_money ← from money.add ^1.0.0 · built alongside by fune
from .money_amount import Money, money ← from money.amount ^1.0.0 · built alongside by fune
ISO_DATE = re.compile(r"[0-9]{4}-[0-9]{2}-[0-9]{2}")
def _rate_on(vehicle: str, on_date: str):
best = None
earliest: Optional[str] = None
for rule in AMAP_RATES:
if rule.vehicle != vehicle:
continue
if earliest is None or rule.valid_from < earliest:
earliest = rule.valid_from
if on_date < rule.valid_from:
continue
if rule.valid_to is not None and on_date > rule.valid_to:
continue
if best is None or rule.valid_from > best.valid_from:
best = rule
if best is not None:
return best
# A history=current build has dropped the old rows; refuse rather than pay an
# old claim at today's rate.
if AMAP_RATES_HISTORY != "full" and earliest is not None and on_date < earliest:
raise ValueError(
"no approved mileage rate for %s on %s: this build was installed with history=%s, "
"so it only carries rates from %s. Reinstall with history=full for older claims."
% (vehicle, on_date, AMAP_RATES_HISTORY, earliest)
)
raise ValueError("no approved mileage rate for %s on %s" % (vehicle, on_date))
def _whole_miles(name: str, value: int) -> None:
if isinstance(value, bool) or not isinstance(value, int) or value < 0:
raise ValueError("%s must be a whole number of miles, not negative, received %s" % (name, value))
def _gbp(name: str, value: Money) -> None:
if value.currency != "GBP":
raise ValueError("%s must be in GBP, received %s" % (name, value.currency))
if value.minor < 0:
raise ValueError("%s must not be negative, received %d" % (name, value.minor))
def _excess_and_shortfall(paid: Money, approved: Money) -> Tuple[Money, Money]:
difference = subtract_money(paid, approved)
if difference.minor > 0:
return difference, money(0, "GBP")
return money(0, "GBP"), money(-difference.minor, "GBP")
def mileage_allowance(
vehicle: MileageVehicle,
previous_miles: int,
miles: int,
passenger_miles: int,
paid: Money,
passenger_paid: Money,
on_date: str,
) -> MileageAllowance:
"""HMRC approved mileage allowance payments for business miles in an
employee's own vehicle.
The 10,000-mile threshold is per tax year, so a claim that crosses it is
split: previous_miles says where in the year this claim starts. Paying a
flat 45p (or 55p) on every mile past 10,000 is the usual mistake; the
excess over 25p is taxable.
"""
if vehicle not in ("car-van", "motorcycle", "bicycle"):
raise ValueError('unknown vehicle "%s": use car-van, motorcycle or bicycle' % (vehicle,))
_whole_miles("previousMiles", previous_miles)
_whole_miles("miles", miles)
_whole_miles("passengerMiles", passenger_miles)
_gbp("paid", paid)
_gbp("passengerPaid", passenger_paid)
if not isinstance(on_date, str) or not ISO_DATE.fullmatch(on_date):
raise ValueError('onDate must be an ISO date (YYYY-MM-DD), received "%s"' % (on_date,))
if vehicle != "car-van" and (passenger_miles > 0 or passenger_paid.minor > 0):
raise ValueError("passenger payments apply only to cars and vans")
rate = _rate_on(vehicle, on_date)
miles_at_first_rate = miles
miles_at_second_rate = 0
if rate.threshold_miles is not None:
first_left = max(0, rate.threshold_miles - previous_miles)
miles_at_first_rate = min(miles, first_left)
miles_at_second_rate = miles - miles_at_first_rate
approved = money(
miles_at_first_rate * rate.first_rate_pence + miles_at_second_rate * rate.second_rate_pence, "GBP"
)
taxable_excess, relief = _excess_and_shortfall(paid, approved)
passenger_approved = money(0, "GBP")
if vehicle == "car-van":
passenger_approved = money(passenger_miles * _rate_on("passenger", on_date).first_rate_pence, "GBP")
# There is no relief for passenger payments below 5p, only tax above it.
passenger_taxable_excess, _ = _excess_and_shortfall(passenger_paid, passenger_approved)
return MileageAllowance(
approved=approved,
paid=paid,
taxable_excess=taxable_excess,
relief=relief,
miles_at_first_rate=miles_at_first_rate,
miles_at_second_rate=miles_at_second_rate,
first_rate_pence=rate.first_rate_pence,
second_rate_pence=rate.second_rate_pence,
passenger_approved=passenger_approved,
passenger_taxable_excess=passenger_taxable_excess,
)