achkit

The ACH file toolkit for developers. Generate, parse and validate NACHA ACH files in a few lines. Fully typed. Zero dependencies. Returns and NOC included. Available for both JavaScript/TypeScript and Python, with byte-identical output across the two.

npm i achkit          pip install achkit

The NACHA format is 94-character fixed-width records, positional fields, blocking factors of ten, and hash totals that must reconcile to the byte. One off-by-one and your ODFI rejects the whole batch. achkit does the counting so you describe intent instead.

JavaScript / TypeScript

import { AchFile, parse, validate } from 'achkit'

const file = AchFile.create({ originDfi: '091000019', companyId: '1234567890' })

file.batch({ sec: 'PPD', description: 'PAYROLL', effectiveDate: '2026-07-22' })
    .credit({ name: 'Jane Doe', routing: '011401533', account: '0072', amountCents: 124050 })
    .debit({ name: 'ACME LLC', routing: '091000019', account: '1899', amountCents: 124050 })

const bytes = file.render()          // balanced batch, hash totals + block padding done
const { ok, errors } = validate(bytes)
const parsed = parse(bytes)          // every field typed, no positional slicing

Python

from achkit import AchFile, parse, validate

f = AchFile.create(origin_dfi="091000019", company_id="1234567890")
b = f.batch(sec="PPD", description="PAYROLL", effective_date="2026-07-22")
b.credit(name="Jane Doe", routing="011401533", account="0072", amount_cents=124050)
b.debit(name="ACME LLC", routing="091000019", account="1899", amount_cents=124050)

data = f.render()
result = validate(data)
parsed = parse(data)

What's inside

• Generate & parse any NACHA file, round-trip safe.
• Reconciliation validator - ABA routing checksum, entry hash, batch and file control totals, blocking factor. Catches what an ODFI rejects on, before the file leaves your machine. Runs on any file, not just ones achkit made.
• Returns & NOC - R-code and C-code lookup for return processing.
• SEC codes - PPD, CCD, WEB, TEL, CTX and single 05 addenda.
• Money is always integer cents. Dates are always YYYY-MM-DD. No floats, no locale surprises.

Hosted API client (paid)

The library is free and local. The hosted API adds what a local library can't - live routing verification against the FedACH participant directory. Get an API key at achkit.com/dashboard.

import { AchkitClient } from 'achkit'

const client = new AchkitClient({ apiKey: 'ak_...' })
const bank = await client.verifyRouting('021000021')
// { routing, checksumValid, found, active, bank: { name, city, state } }

const result = await client.validate(bytes) // reconciliation + live routing checks

from achkit import AchkitClient

client = AchkitClient("ak_...")
bank = client.verify_routing("021000021")
result = client.validate(data)

Pro adds live routing verification + 10,000 validations/month; Ultra is unlimited with return-file monitoring. See achkit.com.

License

MIT