---
id: bai2
version: "0.15.0"
license: MIT
license_treatment: permissive
maintenance: active
---

# bai2 — BAI2 Parser

License: permissive · Maintenance: active · Downloads: 102.8K/mo

## What it is and what it does

bai2 is a Python parser and writer for BAI2 files, the standard format used by banks to report account balances and transactions for cash management. It reads BAI2 data from files, strings, or line-by-line input and returns structured model objects representing the file hierarchy (Bai2File → Group → Account → TransactionDetail). It can also construct and write BAI2 files programmatically.

The library is actively maintained but explicitly notes it is not yet production-ready due to limited test data. It handles parsing errors, unsupported features, and integrity checks via three exception types. Known to work with files from NatWest, RBS, and JP Morgan, though different banks implement the BAI2 spec with variations. Supports custom transaction type codes for bank-specific extensions.

Use it for:

- Parse bank-supplied BAI2 files to extract account balances and transaction details for reconciliation or reporting.
- Integrate bank balance data into accounting or treasury management systems that consume BAI2 format.
- Generate BAI2 files programmatically for cash management data interchange between internal systems and banks.
- Validate BAI2 file integrity by checking control totals and object counts against reported values.
- Handle bank-specific transaction codes by registering custom type codes for non-standard implementations.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Parses and writes BAI2 files, a standard format for bank balance reporting and cash management data exchange.

Yes, if you need to parse or generate BAI2 files and can tolerate Beta status. The library has low install friction, no dependencies, active maintenance, and covers the core use case. However, the maintainers explicitly warn it is not production-ready due to insufficient real-world test data—verify compatibility with your specific bank's BAI2 variant before deploying to production.

## Install

pip install bai2
uv add bai2
poetry add bai2

## Installing bai2

Before you install: Low install friction with no runtime dependencies. Actively maintained; last commit 2026-03-01 with recent version 0.15.0 (2025-11-04) testing on Python 3.10 through 3.14. Development status is Beta.

License in practice: MIT license (permissive) allows use in commercial and private projects with minimal restrictions.

Quickstart:

pip install bai2

from bai2 import bai2

with open('file.bai2') as f:
    bai2_file = bai2.parse_from_file(f)

# or parse from string
bai2_file = bai2.parse_from_string(bai2_data)

Only tested on Python 3.10+, though documented as likely working on 3.7+; requires Python 3.6 or later.

Verify before relying:

- Extent of real-world BAI2 file compatibility beyond NatWest, RBS, and JP Morgan implementations mentioned.
- Current production-readiness status given the library's own note about insufficient test data.
- Whether custom transaction type code overrides (TypeCodes) cover all common bank-specific variations.

## Package facts

- License: MIT (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 102.8K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

bai2 parser, bank balance reporting, cash management file format, bai2 file reader, balance and transaction parsing, banking data interchange, bai2 writer, banking, file-format, data-interchange

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