We built an automated invoicing system.

1. The problem

Every week the practitioner moved between three systems — Acuity Scheduling (bookings), a Google Sheet (per-client rates and payment preferences), and Xero (invoices) — to bill the sessions she’d delivered. About an hour of repetitive lookup-and-paste each Sunday, with three recurring failure modes:

• Double invoices when a booking label hadn’t been updated yet.
• Forgotten receipts after a client paid, eroding the professionalism of the service.
• Sensitive data risk — therapy bookings carry free-text session notes that mustn’t end up on an invoice.

2. What we built

A single form the practitioner opens in her browser. She picks a date range, ticks the sessions she wants to invoice, and clicks Submit. The rest is automatic: the system pulls each booking, looks up the client’s rate and payment preference, deduplicates against anything already raised in Xero, creates correctly-themed draft invoices, and tags every appointment so it can’t be billed twice.

Two background workflows then complete the cycle: one watches Xero for invoices that have been sent, one watches for invoices that have been paid — emailing the client a branded receipt with the PDF attached, reconciling the booking system, and sending the practitioner a short digest of what happened.

3. How it works now

Sunday afternoon, five minutes, three steps:

1. Open the form → tick the week’s sessions → Submit.
2. Open Xero → review the drafts → click Approve & Send.
3. Close laptop.

flowchart LR
    classDef extern fill:#fdfcfb,stroke:#c4873b,stroke-width:1.5px,color:#0a0f0f
    classDef hub fill:#0a0f0f,stroke:#c4873b,stroke-width:1.5px,color:#fdfcfb
    classDef mail fill:#f3f2f1,stroke:#9a9a96,color:#0a0f0f

    A["Acuity
Scheduling"]:::extern
    S["Google
Sheets"]:::extern
    X["Xero"]:::extern

    N["n8n
(3 workflows)"]:::hub

    EC["Client receipt
emails + PDFs"]:::mail
    EP["Practitioner
digest emails"]:::mail

    A <--> N
    S <--> N
    X <--> N
    N --> EC
    N --> EP
      

Three systems read & written through n8n; two outbound email streams keep the client and practitioner in the loop.

Receipts, reconciliation, and the weekly digest land automatically through the week. Sensitive session content never leaves Acuity — the first node in every workflow strips fields that aren’t needed downstream, so they cannot propagate by accident. Booking-system labels act as the spine of the whole system, which means every workflow is fully idempotent: any run can be safely repeated without duplicating anything.