Moneybird Webhooks Skill

When to Use This Skill

• How do I receive Moneybird webhooks?
• How do I verify the Moneybird-Signature header?
• How do I handle sales_invoice_created, sales_invoice_state_changed_to_paid, or contact_created?
• How do I verify a signature with several v1= values during a secret rotation?
• Why is my Moneybird webhook signature verification failing?

Essential Code (USE THIS)

Every Moneybird delivery carries Moneybird-Signature: t=<unix seconds>,v1=<hex>. v1 is the HMAC-SHA256 (hex) of "{t}.{raw_request_body}", keyed with the webhook's secret as-is. The API returns secret only in the response to POST /{administration_id}/webhooks.json; you can reveal it later on the webhook's detail page in Moneybird (after an MFA confirmation). During a secret rotation the header carries one v1= per active secret, so accept the request if any v1 matches.

Verification (Node.js)

const crypto = require('crypto');

// rawBody: Buffer of the exact request bytes (express.raw({ type: '*/*' }), not express.json)
function verifyMoneybird(rawBody, signatureHeader, secret) {
  if (!secret || !signatureHeader) return false;
  let t; const v1 = [];
  for (const part of signatureHeader.split(',')) {          // trim: "t=1, v1=..." is allowed
    const i = part.indexOf('=');
    const key = part.slice(0, i).trim(), value = part.slice(i + 1).trim();
    if (i > 0 && key === 't' && t === undefined) t = value;
    else if (i > 0 && key === 'v1') v1.push(value);          // ignore unknown schemes
  }
  if (!t || !/^\d+$/.test(t) || v1.length === 0) return false;
  // Optional replay window, off by default: retries and replays keep the original timestamp
  const expected = crypto.createHmac('sha256', secret)
    .update(`${t}.`).update(rawBody).digest('hex');
  // 64-hex check first: Buffer.from(x, 'hex') silently truncates invalid hex
  return v1.reduce((ok, d) => (/^[0-9a-f]{64}$/i.test(d) &&
    crypto.timingSafeEqual(Buffer.from(d.toLowerCase()), Buffer.from(expected))) || ok, false);
}

Verification (Python)

import hashlib, hmac, re

def verify_moneybird(raw_body: bytes, signature_header: str, secret: str) -> bool:
    if not secret or not signature_header:
        return False
    t, v1 = None, []
    for part in signature_header.split(","):
        key, sep, value = part.partition("=")
        key, value = key.strip(), value.strip()
        if sep and key == "t" and t is None:
            t = value
        elif sep and key == "v1":
            v1.append(value)
    if not t or not (t.isascii() and t.isdigit()) or not v1:
        return False
    expected = hmac.new(secret.encode(), t.encode() + b"." + raw_body, hashlib.sha256).hexdigest().encode()
    # bytes on both sides: a non-ASCII header value is a 400, not a TypeError/500
    return any(re.fullmatch(r"[0-9a-f]{64}", d, re.I) and hmac.compare_digest(d.lower().encode(), expected)
               for d in v1)

For complete handlers with tests, see examples/express/, examples/nextjs/, examples/fastapi/.

Timestamp window: off by default

Moneybird recommends rejecting a request whose t is more than 5 minutes from your clock. Hookdeck retries and replays resend the original timestamp, so a 5-minute window rejects late retries. The examples therefore skip the freshness check unless you set MONEYBIRD_TIMESTAMP_TOLERANCE_SECONDS to a positive number of seconds (default 0 = off). Moneybird itself retries a non-200 response 10 times with gradually growing intervals, so the same applies without Hookdeck. Use the Idempotency-Key header for deduplication instead. references/verification.md shows exactly where the window can be dropped or widened.

Dispatch on action

The body is JSON with administration_id, webhook_id, webhook_token, entity_type (for example SalesInvoice), entity_id, state, action, and entity (the same JSON the API returns for that record). Dispatch on action, which is one of the event names you put in enabled_events:

If you subscribe to no events, Moneybird falls back to the legacy behaviour (sales invoice state changes only). A group name such as estimate subscribes to every event in that group. See references/overview.md for the full event families and the payload.

Important Headers

Environment Variables

MONEYBIRD_WEBHOOK_SECRET=your_webhook_secret      # `secret` returned by POST /{administration_id}/webhooks.json
MONEYBIRD_TIMESTAMP_TOLERANCE_SECONDS=0           # optional; a positive value opts in to the replay window

Local Development

# Start tunnel (no account needed)
npx hookdeck-cli listen 3000 moneybird --path /webhooks/moneybird

Reference Materials

• references/overview.md - Moneybird webhook concepts, events, payload
• references/setup.md - Creating the webhook through the API and saving the secret
• references/verification.md - Signature details, rotation, the timestamp window, and debugging