bankstatementparser-loader-mt942: SWIFT MT942 loader

Parse SWIFT MT942 Interim Transaction Report files into bankstatementparser Transaction objects. A single load_mt942(text) call returns a list of bankstatementparser.transaction_models.Transaction, ready for every downstream consumer that already works with the core library's parser output (deduplication, categorisation, exports).

The core bankstatementparser library parses PDF and CSV statements but does not understand the SWIFT MT942 wire format. This loader fills that gap without changing the core data model.

Contents

• Overview
• Install
• Quick Start
• Supported Fields
• Field Mapping
• Summaries
• Errors
• Examples
• When not to use this loader
• Development
• Security
• Documentation
• License
• Contributing
• Acknowledgements

Overview

bankstatementparser-loader-mt942 is a small, focused companion to the bankstatementparser library. It does one thing well: parse the SWIFT MT942 Interim Transaction Report grammar and hand back the same Transaction objects the core PDF/CSV parsers produce. Every transaction is stamped with source="mt942" so you can tell where it came from.

MT942 is an interim statement. Unlike MT940 it carries no :60F: opening or :62F: closing balance — it reports a floor limit, an optional date/time stamp, the statement lines accumulated so far, and debit/credit summaries. This loader models that structure faithfully and never invents balances that are not present in the source.

Install

bankstatementparser-loader-mt942 runs on macOS, Linux, and Windows and requires Python 3.10+ and pip. It pulls in bankstatementparser (>= 0.0.11) automatically.

pip install bankstatementparser-loader-mt942

Quick Start

from bankstatementparser_loader_mt942 import load_mt942

mt942 = """:20:MT942REF001
:25:COBADEFFXXX/DE89370400440532013000
:28C:42/1
:34F:EURD0,00
:34F:EURC0,00
:13D:2506241200+0100
:61:2506240624C500,00NTRFINV-123//BANKREF1
:86:Incoming payment for invoice 123
:61:2506240624D200,50NTRFRENT//BANKREF2
:86:Monthly rent debit
:90D:1EUR200,50
:90C:1EUR500,00
-
"""

transactions = load_mt942(mt942)

for txn in transactions:
    print(txn.value_date, txn.currency, txn.amount, txn.description)
# 2025-06-24 EUR 500.00 Incoming payment for invoice 123
# 2025-06-24 EUR -200.50 Monthly rent debit

Those are bankstatementparser.transaction_models.Transaction objects — debit lines carry a negative amount, credit lines a positive one, and amounts are exact Decimal values (SWIFT's comma decimal separator 500,00 is converted to Decimal("500.00")).

To read from a file instead of a string:

from bankstatementparser_loader_mt942 import load_mt942_file

transactions = load_mt942_file("statement.mt942")

Supported Fields

Unrecognised tags (and the trailing - end-of-message marker) are silently ignored, so future SWIFT additions do not break parsing — this follows Postel's law: be liberal in what you accept. A malformed :61: statement line is skipped rather than fatal, so one bad row never aborts the whole parse.

Real-world wire-format constructs

Genuine bank/SWIFT exports are messier than the tidy sample above. The loader handles the following (pinned by a golden test over a real, third-party fixture in tests/fixtures/real/, whose source, licensing, and provenance are documented in tests/fixtures/real/PROVENANCE.md):

• SWIFT message envelope. Messages wrapped in the header blocks {1:...}{2:...}{3:...} and the text block {4: … -} are unwrapped before parsing; the envelope is never mistaken for content.
• Amounts with no fractional digits. A SWIFT amount may end on the decimal comma with nothing after it: 5000, → Decimal("5000"), 0, → Decimal("0").
• :34F: with an embedded D/C indicator. :34F:NZDC0, yields currency NZD regardless of the C/D letter.
• Multi-line :86:. Continuation lines that do not start with a :tag: head (e.g. /BAI/…, /BENM/…, /ACNO/…) are appended to the :86: description, newlines preserved.
• Supplementary details after :61:. A line immediately following a :61: (before any :86:), such as a bare Transfer or wording/NBKT, is the SWIFT supplementary-details subfield. It is folded into the transaction's description (supplementary text first, then the :86: content, joined by newlines) and never glued onto the statement-line tail — so the parsed transaction_id / reference stay clean. A :61: with supplementary details but no following :86: keeps that text as its description.

Field Mapping

Each :61: statement line becomes one Transaction:

The two-digit YY year uses the standard SWIFT sliding window: 00-79 map to 20YY, 80-99 to 19YY.

Summaries

When you want the message metadata and the :90D:/:90C: roll-ups rather than the individual transactions, call summarize_mt942:

from bankstatementparser_loader_mt942 import summarize_mt942

summary = summarize_mt942(mt942)
print(summary.reference)          # MT942REF001
print(summary.currency)           # EUR
print(summary.debit_count)        # 1
print(summary.debit_sum)          # Decimal("200.50")
print(summary.credit_sum)         # Decimal("500.00")
print(summary.transaction_count)  # 2

Mt942Summary is a frozen dataclass with reference, account_id, currency, statement_datetime, debit_count, debit_sum, credit_count, credit_sum, and transaction_count. Optional fields (no :90x: / :13D: present) default to None.

Errors

A payload missing the mandatory :20: reference or :25: account identification raises ValueError with a message naming the missing tag:

load_mt942(":25:ACC\n:61:250624C10,00NTRFX\n")
# ValueError: MT942 payload missing required :20: reference

Examples

Two runnable examples live in examples/:

• 01_load_mt942.py — parse a small MT942 string into transactions.
• 02_summarize_mt942.py — read a file and print the Mt942Summary roll-ups.

Both are exercised in CI on every commit.

When not to use this loader

• You have a PDF or CSV statement. Use the core bankstatementparser parsers directly — this loader is only for the SWIFT MT942 wire format.
• You have MT940 (final statements with balances). MT940 is a different message; this loader handles the interim MT942 report. The :61: / :86: grammar is shared, but MT942 has no :60F: / :62F: balances.
• You need bank-specific :86: sub-field parsing (e.g. Deutsche Bank's ?20 / ?30 / ?32 GVC codes). The raw :86: value is preserved verbatim as the transaction description; downstream tooling can parse it if needed.
• Your MT942 is PGP / GPG encrypted. Decrypt upstream and pass the plaintext to the loader.

Development

git clone https://github.com/sebastienrousseau/bankstatementparser-loader-mt942
cd bankstatementparser-loader-mt942
python -m venv .venv && source .venv/bin/activate
pip install -e .
pip install pytest pytest-cov ruff mypy interrogate
pytest --cov=bankstatementparser_loader_mt942 --cov-branch --cov-fail-under=100
ruff check bankstatementparser_loader_mt942 tests examples
mypy bankstatementparser_loader_mt942
interrogate -c pyproject.toml bankstatementparser_loader_mt942

Security

bankstatementparser-loader-mt942 parses a flat text format with no XML envelope, so the XXE / billion-laughs surface does not apply. Field regexes are anchored and bounded, so catastrophic backtracking is not a concern. Reporting practice and supported versions are documented in SECURITY.md. Vulnerabilities go via GitHub Private Vulnerability Reporting, not public issues.

Documentation

• README.md — this file
• ARCHITECTURE.md — codebase map
• CHANGELOG.md — release notes
• ROADMAP.md — what's next
• SECURITY.md — disclosure + supported versions
• examples/ — runnable scripts, exercised in CI

License

Licensed under the Apache License, Version 2.0. Any contribution submitted for inclusion shall be licensed as above, without additional terms.

Contributing

Contributions are welcome. Open an issue or PR on the repository.

Acknowledgements

Built on the bankstatementparser library. The MT942 grammar follows the SWIFT User Handbook MT942 Interim Transaction Report specification and the common-denominator subset shipped by major EU and UK commercial banks.