HubSpot to Xero invoicing across 3 legal entities and 4 currenciesHubSpot to Xero invoicing across 3 legal entities and 4 currencies

A software reseller trades through three legal entities in the US, the UK and the EU, each with its own Xero organisation. Sales run in HubSpot. Customer payments had been collected through the CRM's own payments product, with fees on every invoice.

What was broken

Sales ran in HubSpot, the books in three Xero organisations. The manual route from the CRM into the ledgers had broken after a change of accountant, and customer payments went through the CRM's own payments product, with fees on every invoice.

What it cost

• Fees on every invoice paid through the CRM's payments product.
• Deals re-keyed by hand into three ledgers, in four currencies, with different account codes per entity.
• An invoice that is never raised is revenue that is never collected.

The brief

Turn every Closed Won deal into a correct draft invoice in the right Xero organisation and currency, route it through finance approval, email the customer without landing in spam, and chase payment, without anyone re-keying a deal.

• Three ledgers, four currencies, different account codes per entity.
• Finance must approve every invoice before a customer sees it.
• Deals with several invoices are normal, so duplicates must be impossible, not just unlikely.
• A clear scope rule agreed with the business: only Closed Won deals with a HubSpot invoice attached.

• Architect and builder of the system.
• Delivered directly, billed through M.A. Whately & Co., not through Upwork.
• Scope rule agreed with the business up front: only Closed Won deals with a HubSpot invoice attached.
• Finance stays the approver: nothing reaches a customer without its sign-off.

1. 00

   Before

   The manual route into Xero broken, and payment fees on every invoice.

2. 01

   Feb 2026

   Designed: one CRM, three Xero organisations, four currencies, and the scope rule.

3. 02

   Pre-launch

   Audit of the build: 9 bugs found and fixed (2 critical), 18 edge cases covered, a 15-item go-live checklist green.

4. 03

   15 Apr 2026

   Live in production.

5. 04

   Apr to Sep 2026

   Steady state at about 52 invoices a month; 212+ processed by September.

6. 05

   In production

   A wrong EU revenue account code in place since go-live found and corrected, with about EUR 42K flagged for reclassification. A proposed bulk void list of about USD 20.8K held back as unsafe.

7. 100

   15 Sep 2026

   Hardening release, shipped with a 49-assertion test harness.

What was built

• Eight n8n workflows, 119 nodes: a router, a deal-bundle fetcher, a transformer, a Xero draft creator, an approval watcher, payment reminders, a retry queue and a global error handler.
• Signed approvals. Finance approves through HMAC-signed links; the watcher verifies the signature before anything is sent.
• Idempotency and a dead-letter queue. State lives in Supabase, every write is keyed, and failed jobs retry up to five times before landing in a queue a human reviews.
• Customer email via the company's own mailbox rather than the ledger's mailer, to stay out of spam folders. Reminders at 7 days before, on the due date, and 14 days overdue.

• Finance approves through HMAC-signed links; the watcher verifies the signature before anything is sent.
• HMAC-SHA256 on the Xero webhook, idempotency through a payload hash and a unique index on the invoice ID, so a retry never doubles an invoice.
• Failed jobs retry up to five times, then land in a dead-letter queue a person reviews.
• Invoices routed by currency to the right legal entity; UK VAT applied on GBP invoices only.
• The system flags, a human decides: an unsafe bulk void list was held back, not executed.

How it was tested

A 49-assertion test harness shipped with the September hardening release. In production, a wrong EU revenue account code that had been in place since go-live was found and corrected, with about EUR 42K flagged for reclassification. A proposed bulk void list of about USD 20.8K was held back because it was unsafe: the system flags, a human decides.

• The workflows, the state database and the credentials, in the client's own accounts.
• A runbook, the deploy procedure, the go-live checklist and the test harness.

• n8n
• HubSpot API
• Xero API (3 tenants, OAuth2)
• Supabase (PostgreSQL)
• HMAC webhooks
• Microsoft Outlook

1. Upwork review5 out of 5 stars

   Great professional. Fast, smart, clear. Already doing a new contract with him to keep working.