Automating Invoicing and Dunning for London SMBs: Cost and ROI 2026

The verdict in three sentences

For a services SMB with EUR 5M to 20M in revenue, automating invoicing and dunning costs between EUR 5,000 and 20,000 excluding VAT in 2026 (roughly GBP 4,300 to 17,000), first-year software subscriptions included. The payoff is first and foremost cash: every day of DSO you cut frees about EUR 27,000 per EUR 10M of revenue, and a well-scoped project removes 10 to 20 days. E-invoicing mandates (France from September 2026, the UK consulting on mandatory e-invoicing from 2029, Peppol spreading across Europe) make this project unavoidable for anyone trading in Europe, so you might as well turn it into a real cash gain rather than a compliance exercise.

What automation really costs in 2026

The budget depends mainly on three factors: the number of invoices issued per month, the quality of the data in your ERP or accounting software, and how customised your dunning scenarios need to be. Here are the ranges we see for a services SMB.

A light project (under 300 invoices a month, a well-configured SaaS tool) lands around EUR 5,000 to 8,000. A project with several entities, complex recurring contracts and a legacy ERP climbs towards EUR 15,000 to 20,000. Average lead time is 6 to 10 weeks.

What you gain: DSO, time and compliance

The return comes from three combined sources. The largest is released cash, which many owners underestimate because it never shows up in the P&L.

On the legal side, UK law (Late Payment of Commercial Debts Act) lets you claim statutory interest at 8 % above base rate plus fixed compensation of GBP 40 to 100 per invoice, and France applies a fixed EUR 40 fee per late invoice. A tool that calculates them automatically turns an often ignored right into revenue. Choosing an e-invoicing-ready billing tool now also avoids a second migration later.

Pitfalls to avoid before you sign

First pitfall: automating reminders on dirty data. If billing contacts, payment terms or PO numbers are wrong in the ERP, the tool will simply send wrong reminders faster. Plan 1 to 2 weeks of clean-up. Second pitfall: one tone for every customer. A key account on 60-day terms is not chased like a micro-business on 30 days; segment into at least three groups. Third pitfall: forgetting people. The best results come from a scenario where the tool prepares and sends reminders at D+1, D+10 and D+20, then creates a call task for the credit controller at D+30.

Mini case study

Sarah, CFO of an engineering consultancy in London (EUR 11M in revenue, 420 invoices a month), has a 72-day DSO. Her average receivables therefore reach 11,000,000 × 72 / 365 ≈ EUR 2.17M. She launches a EUR 12,500 project (ERP connector, e-invoicing network, three-segment dunning, bank reconciliation), plus EUR 250/month in subscriptions.

After six months, DSO drops to 57 days: 15 days gained × EUR 30,100 per day ≈ EUR 452,000 of cash released. On an overdraft facility at 6 %, the interest saving is about EUR 27,000 a year. Add 3.5 person-days of invoicing saved per month, about EUR 13,000 a year in loaded cost. The project pays back in under four months.

FAQ

Does e-invoicing force me to change tools in 2026?

Not necessarily. France requires all companies to receive e-invoices from 1 September 2026 and SMBs to issue them from 1 September 2027, and the UK plans a mandate from 2029. If your current software connects to a Peppol access point or certified platform, a EUR 1,000 to 4,000 connector is enough.

How many days of DSO can you realistically cut?

Between 10 and 20 days in most services SMBs that started with no structured dunning. Beyond that, you need to work on contract terms and milestone billing, not just the tool.

Do automated reminders damage customer relationships?

Not if they are well written and segmented. A courtesy reminder at D-5 before the due date alone reduces late payments by 15 to 25 % according to field feedback, and most customers see it as a service.

How long until we are live?

Allow 6 to 10 weeks: 1 to 2 weeks of scoping and data clean-up, 3 to 5 weeks of integration, and 2 weeks of testing with a sample of customers.

SaaS tool or custom development?

A SaaS tool is enough below 300 invoices a month with a standard ERP. Custom work makes sense with several entities, complex recurring contracts or an industry ERP without a proper API, for a budget of EUR 12,000 to 20,000.

Let's scope your project. Send us your monthly invoice volume, your ERP and your current DSO: we will price the scope (EUR 5,000 to 20,000 depending on complexity) with a 6 to 10 week go-live. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.