All articlesGuide

Building Invoice Approval Workflows That Scale

When you're a solo founder, you approve every invoice yourself. As your team grows, that doesn't scale — and neither does a shared inbox. Here's how to build an approval workflow that works at any size.

10 March 20256 min read

Why approval workflows matter

An invoice approval workflow ensures every purchase is reviewed before it's paid. Without one, invoices can be paid twice, fraudulent invoices slip through, or legitimate expenses get rejected after payment. A good workflow adds a lightweight checkpoint without creating bureaucracy.

The three levels of approval sophistication

1

Single approver (0–5 employees)

One person reviews all invoices. Works fine at low volume. The key is making this fast — ideally a mobile-friendly queue rather than digging through email.

2

Rules-based auto-approval (5–20 employees)

Trusted suppliers under a certain amount are approved automatically. Everything else goes to a reviewer. Reduces touchpoints by 70-80% without adding risk.

3

Multi-tier approval (20+ employees)

Invoices over £X require a second approver. Certain categories (capital expenditure, new suppliers) always need finance team sign-off. Larger organisations may use ERP systems.

Auto-approval rules: what to configure

  • Supplier whitelist — known, trusted suppliers auto-approve
  • Amount threshold — invoices under £500 from approved suppliers auto-approve
  • Category rules — recurring SaaS subscriptions always auto-approve
  • Duplicate detection — flag any invoice number seen in last 12 months
The goal isn't to remove humans from the process — it's to focus human attention on invoices that actually need it. Most routine supplier invoices need zero review time.

Set up smart approval rules in InboxBill

Configure auto-approval for trusted suppliers and focus on what matters.

Try InboxBill free