GST review

Distribution gst-review, import package gstreview. Library only: this component ships no command.

Package lifecycle: published. Install gst-review from PyPI with pip install gst-review; see release notes and DISCLAIMER.md.

Review aids for Australian GST over bank and ledger lines, for bookkeepers and accountants checking a coded bank feed before a BAS and reconciling a lodged BAS after it. The engines read the figures you supply, contact no service, write to no ledger and lodge nothing. They are experimental review aids, not advice or return preparation.

Ryan Duguid is not a registered tax agent or BAS agent. Project support is limited to software issues reproduced with fabricated data. Do not send taxpayer information.

Coding review

review_coding gives every bank line one review state and the reason for it:

States are checked in that order, so a registration conflict shows even on a confirmed line. Lines pair one to one across entities, nearest date first, within match_window_days (default 3, at most 31).

A negative amount is money out. The GST code on the line, or else the suggested code, is read through a code table. The default covers common Xero and MYOB AU codes; pass gst_codes to use your own, mapping each code to taxable, gst_free, input_taxed or outside_gst.

from datetime import date
from decimal import Decimal

from gstreview import BankLine, Registration, review_coding

result = review_coding(
    [
        BankLine("1", "Alder Pty Ltd", date(2026, 8, 3), Decimal("-110.00"),
                 account="Repairs", gst_code="GST", confirmed=True,
                 supplier_registered=False),
        BankLine("2", "Alder Pty Ltd", date(2026, 8, 4), Decimal("-5000.00")),
        BankLine("3", "Birch Trust", date(2026, 8, 5), Decimal("5000.00")),
        BankLine("4", "Birch Trust", date(2026, 8, 6), Decimal("330.00"),
                 suggested_account="Rent", suggested_gst_code="GST"),
    ],
    {"Alder Pty Ltd": Registration(date(2024, 7, 1)), "Birch Trust": Registration(None)},
)
for row in result["lines"]:
    print(row["id"], row["state"])

1 gst_differs_from_registration
2 between_entities
3 between_entities
4 gst_differs_from_registration

The result also carries counts by state, facts_used (registration dates, match window and code table), not_decided, sources and source_checked.

The review does not decide whether an entity was required to be registered (s 23-5), whether a supply is taxable, GST-free or input taxed on its merits, what a transfer between entities is, or whether a suggestion is right. Refunds, reversals and creditable importations are not distinguished from other lines.

BAS reconciliation

reconcile_bas works out G1, G2, G3, G10, G11, 1A and 1B from ledger lines for each tax period and compares them with the lodged figures. Each label gets a status: matches, differs (with the difference and the lines behind the ledger figure), not_reported (no lodged figure for that label) or negative_ledger (credit notes exceed sales or purchases; a BAS takes no negative figures).

• Attribution. On the cash basis a line falls in the period of its payment date. On accruals it falls in the period of the earlier of its invoice and payment dates (GST Act ss 29-5 and 29-10). A period's timing list names lines invoiced in it but attributed elsewhere, or still unpaid on the cash basis.
• Rounding. Ledger totals are rounded down to whole dollars before comparison, as the ATO's BAS instructions require. Lodged figures must be whole non-negative dollars.
• GST-inclusive or not. G labels include GST unless g1_includes_gst=False; the ATO requires every other label to follow the choice made at G1.
• Codes. Each line has a side (sale or purchase) and a GST code, read through a code table into a category: taxable, capital, gst_free, capital_gst_free, export, input_taxed or excluded. The default covers common Xero and MYOB AU codes; pass bas_codes to use your own. Excluded lines are listed in each period's kept_out. A line in a period that cannot be placed (an unknown code, a capital code on a sale, GST on a GST-free code) refuses the whole reconciliation, naming every such line and the reason, because a label compared without it could show matches wrongly.

The result also lists periods with ledger lines but no lodged figures (not_lodged), lodged periods with no ledger lines (no_ledger_lines), lines outside every period and unpaid lines.

from datetime import date
from decimal import Decimal as D

from gstreview import LedgerLine, Period, reconcile_bas

lines = [
    LedgerLine("inv-101", "sale", D("1100.00"), D("100.00"), "GST", date(2026, 7, 14),
               date(2026, 7, 30)),
    LedgerLine("inv-102", "sale", D("550.00"), D("50.00"), "GST", date(2026, 9, 25),
               date(2026, 10, 6)),
    LedgerLine("bill-7", "purchase", D("330.00"), D("30.00"), "GST", date(2026, 8, 2),
               date(2026, 8, 2)),
]
result = reconcile_bas(
    lines,
    [Period("2026-Q1", date(2026, 7, 1), date(2026, 9, 30))],
    {"2026-Q1": {"G1": D(1650), "1A": D(150), "1B": D(30)}},
    basis="cash",
)
for label, row in result["periods"][0]["labels"].items():
    if row["status"] != "not_reported":
        print(label, row["status"], row["difference"], row["lines"])
print("timing", result["periods"][0]["timing"])

G1 differs -550 ['inv-101']
1A differs -50 ['inv-101']
1B matches None []
timing ['inv-102']

The lodged figures here include invoice inv-102, which was paid in the next quarter. On the cash basis it belongs to that quarter, so G1 and 1A differ and the period's timing list names it.

It does not decide whether a difference needs a revised BAS, whether any code is right, or which basis applies (s 29-40). Part payments on the cash basis need one line per payment. Labels other than those above, adjustments and GST on imports are out of scope.

Aus Accounting MCP

Aus Accounting MCP exposes both reviews as the review_gst_coding and reconcile_bas tools, taking decimal strings and YYYY-MM-DD dates, from the published distribution it pins.