The invoicing screen demos well. Ask what's inside the PDF

Watch enough field-service software demos and the invoicing section blurs into one: an itemised invoice appears, the logo sits top-right, someone clicks send, and a Xero or Sage logo earns its cameo. It all looks the same because, on screen, it mostly is the same. The differences that will matter over the next three years are the ones a demo cannot show, because they live inside the PDF and underneath the data model.

We spent a while this summer reading how invoicing gets marketed across this industry, and the pattern is striking: it is sold almost entirely as speed and cashflow. Get paid faster, chase less, invoice from the van. All real benefits — we make some of the same arguments ourselves. What almost nobody mentions is that the UK confirmed in November 2025 that VAT invoices must be issued as e-invoices from April 2029, or that half of Europe already requires structured invoices today. The invoice is becoming a regulated data object, and the marketing hasn't noticed yet.

So ask the questions the demo skips. Five of them, four minutes, and the answers separate a data model from a screen.

• Is the invoice PDF also an e-invoice? Specifically: is it a PDF/A-3 with the invoice data embedded as structured XML to the EN 16931 standard — the European standard the mandates are built on — or is it a print of the screen? "We email a professional PDF" was a complete answer in 2023. It no longer is.
• Who validates the invoice data, and when? A structured invoice is only useful if the data in it is right, and EN 16931 carries a rulebook of around two hundred business rules. The strong answer is per-document validation before anything goes out. The weak answer is silence, because most systems have never had a rulebook to validate against.
• What happens to the number series when an invoice is wrong? If the answer involves deleting it, walk. Deleted invoices are how sequences grow holes an inspector asks about. The right shape: issued invoices are frozen, corrections happen through new documents, and a cancelled invoice keeps its number so the series explains itself.
• Can a line's VAT rate contradict its VAT code? Type a zero-rated line and then type 20% against it. If the system accepts that, the VAT column is decoration, and the errors it lets through become your accountant's problem at quarter end.
• What is the 2029 plan? Fair warning: nobody can honestly claim readiness for the UK mandate yet — the format standard won't be named before the government's roadmap this autumn. What you are listening for is whether the vendor's answer is "software update" or "migration project". A system whose invoices already carry structured data gets to 2029 by changing how invoices travel. A system that stores flat documents has to rebuild what an invoice is.

The fifth question hides the expensive part. History does not retrofit: an invoice issued as flat text stays flat text, and no deadline-week scramble converts three years of PDFs into structured records. Whatever you choose, the day it starts issuing structured invoices is the day your compliant history starts accumulating — which argues for that day arriving well before April 2029.

There is a sixth question you might be tempted to skip: won't the accounting package sort all this out? Partly, and with strings. Xero can already send e-invoices in the UK, but only between VAT-registered businesses and only when the customer is already registered on the Peppol network; otherwise it falls back to a PDF. QuickBooks has shipped structured e-invoicing where mandates already bite, Malaysia first, not yet the UK. Sage's e-invoicing push points at the 2029 mandate, with today's shipped capability sitting in its larger products. None of that is criticism; ledgers move at ledger speed. But it settles the buying question, because no ledger can e-invoice a document it never raises. If your invoices are raised in your job platform, which is rather the point of having one, the moment of issue never touches the ledger, and the e-invoice has to be born where the invoice is.

For the record, our own answers: BlueWave invoices go out as Factur-X e-invoices at the EN 16931 profile, each validated against the official rulebook before it goes out; numbers are allocated at issue, issued invoices are frozen, voids keep their numbers; and VAT rates are derived from VAT codes, so the contradiction in question four cannot be typed. Ask us the five anyway — we published them knowing our own answers, and any vendor should sit the same exam. The rest of what a demo won't show you, from exit terms to seat pricing at twice your headcount, has its own checklist.