finance.tax.remove-vat Unreviewed

def remove_vat(gross: Money, jurisdiction: str, category: str, on_date: str) -> VatBreakdown

from fune.finance.tax.remove_vat import remove_vat  # finance.tax.remove-vat@^1

from .finance_tax_add_vat import VatBreakdown  ← from finance.tax.add-vat ^1.0.0 · built alongside by fune
from .finance_tax_vat_rate import vat_rate  ← from finance.tax.vat-rate ^1.0.0 · built alongside by fune
from .math_round_div import round_div  ← from math.round-div ^1.0.0 · built alongside by fune
from .money_amount import Money, money  ← from money.amount ^1.0.0 · built alongside by fune


def remove_vat(gross: Money, jurisdiction: str, category: str, on_date: str) -> VatBreakdown:
    """Extract the VAT already included in a gross amount.

    Taking 20% off a gross price is the classic error: the VAT inside a 120.00
    gross price is 20.00, not 24.00. The net is gross x 10000 / (10000 + rate),
    and the tax is the remainder, so the parts always add back to exactly the
    gross with no stray penny.
    """
    rate = vat_rate(jurisdiction, category, on_date)
    net = money(round_div(gross.minor * 10000, 10000 + rate.basis_points, "half-up"), gross.currency)
    return VatBreakdown(
        net=net,
        tax=money(gross.minor - net.minor, gross.currency),
        gross=gross,
        basis_points=rate.basis_points,
    )

Install

fune build

With that line in your source, in a Python project (language python in fune.project), fune build resolves it and its 4 dependencies, pins them in fune.lock, downloads only the Python package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add finance.tax.remove-vat

The manifest, vectors and README with only the Python implementation. Install it without the registry with fune add ./finance.tax.remove-vat-1.0.2-python.fune, or fetch it from a terminal with fune pull finance.tax.remove-vat@1.0.2:python.

The whole function, every language, is one file too: finance.tax.remove-vat-1.0.2.fune, 12,741 bytes, sha256 a0de006f7150d4162a1c9fbb6fdb42ac78bf05e9a21abf97409fe209e8e6bb88. It installs into a project of any language.

# fune: before finance.tax.remove-vat

# fune: after finance.tax.remove-vat

# fune: replace finance.tax.add-vat in finance.tax.remove-vat
# fune: replace finance.tax.vat-rate in finance.tax.remove-vat
# fune: replace math.round-div in finance.tax.remove-vat
# fune: replace money.amount in finance.tax.remove-vat

# fune: step finance.tax.remove-vat after <n|label>

More from the author

1.0.1 adds tests; behaviour unchanged.

## Before you rely on this

**Not professional advice.** This capability calculates tax figures from published rules. It is a software component for developers, not tax advice. Rules change and every rate here has an effective date. Check that the dates cover your case. Verify results against the official sources listed above, and have a chartered accountant or tax adviser review how you use it, before anyone relies on the output. Provided "as is" under its licence, without warranty.

**Unreviewed.** This capability's implementations agree in every language and pass its published test vectors, which were worked out from the official sources cited. But no qualified chartered accountant or tax adviser has yet checked those vectors, or confirmed that the capability covers the cases it claims. Treat it as a draft. Do not use it for real people, money or decisions without your own expert review. Once a qualified reviewer signs off, this notice is replaced with their name, qualification and the date. Each new version needs fresh sign-off.

1.0.2 marks it unreviewed. The code and the tests are unchanged.

Files