BankingStandards

Tagline: "Building the foundation for seamless financial transactions in Elixir."

An Elixir library for parsing, generating, and validating financial and payment file standards. Currently ships with NACHA ACH support; Canadian (RTR, Interac, CPA AFT) and ISO 20022 rails are on the roadmap.

What ships today

NACHA ACH (United States), read and write:

• BankingStandards.ACH.Parser — parse/1 reads a file from disk, parse_string/1 parses an in-memory string. Both return {:ok, %AchFile{}} with a hierarchical structure (AchFile → [Batch → [{EntryDetail, [Addenda]}]]) or {:error, reason} for files with records out of sequence or bad line lengths.
• BankingStandards.ACH.Generator — generate/1 serializes an AchFile back to the 94-character fixed-width NACHA format with proper block padding. write/2 writes the result to a path. Round-trip identity holds (parse → generate → parse).
• BankingStandards.ACH.Validator — validate/1 cross-checks batch trailers and the file control against the actual entries (entry hash, counts, dollar sums, block count) and verifies every routing number's ABA check digit. valid_routing_number?/1 is exposed for direct use.

Addenda are typed by addenda type code: Addenda05 (payment-related info), Addenda02 (POS terminal), Addenda98 (Notification of Change), Addenda99 (return). IAT addenda (types 10–18) are not yet supported.

Roadmap

In priority order:

1. Full NACHA coverage — SEC code enum (PPD, CCD, WEB, TEL, CIE, CTX, ARC, BOC, POP, RCK, IAT) with per-SEC validation, transaction code semantics, return entries (R-codes), Notification of Change (C-codes), prenotifications.
2. ISO 20022 XML foundation — saxy-based parser/generator for ISO 20022 envelopes. Reusable across RTR, future SEPA, future Fedwire ISO migration.
3. Canadian Real-Time Rail (RTR) — pacs.008 / pacs.002 / camt.056 messages with the Payments Canada profile constraints layered on top of the generic ISO 20022 modules.
4. Interac — research spike to identify what's actually standardized (versus bank-API mediated) before any code lands.
5. CPA AFT (EFT 005) — legacy Canadian batch rail, 1464-byte fixed-width records, same hierarchical pattern as ACH.

Installation

Add banking_standards to your list of dependencies in mix.exs:

def deps do
  [
    {:banking_standards, "~> 0.1.0"}
  ]
end

Usage

Parsing

alias BankingStandards.ACH.Parser

{:ok, ach_file} = Parser.parse("path/to/file.ach")

ach_file.header.immediate_destination
# => "076401251"

ach_file.batches
|> Enum.flat_map(& &1.entries)
|> Enum.map(fn {entry, _addenda} -> entry.amount end)
# => [10000, 5000, ...]

Generating

alias BankingStandards.ACH.Generator

Generator.write(ach_file, "out.ach")
# or, to get the string:
contents = Generator.generate(ach_file)

The generator writes trailer and control values verbatim — it does not recompute them. Run Validator.validate/1 first if values may be inconsistent.

Validating

alias BankingStandards.ACH.Validator

case Validator.validate(ach_file) do
  :ok ->
    :ok

  {:error, errors} ->
    # errors is a list of human-readable strings, one per rule violation
    Enum.each(errors, &IO.puts/1)
end

Validator.valid_routing_number?("011000015")
# => true

Contributing

Issues and PRs welcome. The pre-commit gate is mix format --check-formatted, mix compile --warnings-as-errors, mix test, mix credo --strict, mix ex_dna, mix dialyzer.

License

MIT. See the LICENSE file.