Switching your own systems to e-invoicing is the easier half of the job. Getting your suppliers to send invoices in the right format — consistently, without errors — is where most AP automation projects stall. The technology is usually not the problem. The problem is that suppliers have their own systems, their own workflows, and varying degrees of willingness to change.
This post covers a practical approach to supplier onboarding that works whether you have 20 suppliers or 2,000.
Start with data, not a rollout plan
Before contacting anyone, pull a report of your supplier base segmented by invoice volume. You will typically find that around 20% of your suppliers send 80% of your invoice volume. Those high-volume suppliers are where e-invoicing will have the most impact — and where it is worth investing significant onboarding effort.
The remaining 80% of suppliers, who send occasional low-value invoices, may not justify a complex integration. For them, a simpler path — a web portal where they can enter invoices manually, or a standard email-to-process flow for PDF — may be the right answer rather than forcing them onto PEPPOL or eBill.
Knowing this before you start lets you design two or three tiers of onboarding rather than one-size-fits-all.
Segment your suppliers
A workable segmentation for most Swiss companies:
Tier 1 — High-volume, ERP-connected suppliers. These are your major recurring suppliers: raw material vendors, logistics providers, large service firms. They send tens or hundreds of invoices per month. For these suppliers, a direct PEPPOL or eBill integration makes sense. They likely already have some e-invoicing capability or are actively building it.
Tier 2 — Medium-volume suppliers without ERP integration. These suppliers send a meaningful number of invoices — say, 10 to 50 per month — but may not have an ERP with PEPPOL support. For them, access point providers with a web portal or SFTP-based XML upload are often the right fit. The cost of integration is low enough to be worth it.
Tier 3 — Low-volume or one-time suppliers. A supplier who sends you three invoices a year does not need a PEPPOL integration. A PDF-to-process workflow with OCR, or a supplier self-service portal where they enter invoice data manually, is more appropriate. Do not try to drag every supplier onto the same infrastructure.
The initial communication
The first message to suppliers should answer three questions they will immediately have: what are you asking them to do, why, and what does it cost them?
A practical first contact letter:
Subject: Request to submit invoices electronically — Company name
We are updating our accounts payable process to handle invoices electronically. From date, we would like to receive your invoices via PEPPOL / eBill / our supplier portal.
This change costs you nothing. If you already use an ERP system, your software provider can likely enable this in a configuration step. If not, we can provide access to a free web portal where you can enter invoice data directly.
To get started, please contact name at email by date. We will send you the technical details and answer any questions.
Short. No jargon. No long list of format specifications in the first message. Those come later, for the suppliers who ask.
What to send to ERP-connected suppliers
For Tier 1 and 2 suppliers who have their own ERP or accounting software, they need:
- Your PEPPOL participant ID (
0209:CHE...) so they can address invoices to you - Your eBill biller ID if you use eBill
- A list of mandatory fields you require: PO reference, cost centre if applicable, your UID as buyer
- A sample of a correct invoice in the expected format (or a link to the SwissDIGIN specification)
- Contact details for technical questions
Suppliers whose software supports PEPPOL natively will often be live within a week of receiving this information. The main thing to check is that their first test invoice validates correctly before you start receiving production invoices — the SwissDIGIN validation tool is useful here.
Common supplier objections and how to handle them
"Our software doesn't support PEPPOL." Check with their software vendor first — support may exist as an optional module or update. If it genuinely does not, offer the web portal or SFTP XML upload path. Very few suppliers are completely blocked.
"This will take too long to set up." Offer to set a realistic deadline — 30 or 60 days — and provide a dedicated contact who can help with questions. Most ERP integrations take a day or two of configuration once the supplier's IT team picks it up. The delay is almost always scheduling, not effort.
"We don't want to change our invoicing process." For low-volume suppliers, accept PDF for now. For high-volume ones, you may need to use a harder lever: some companies inform strategic suppliers that they will no longer accept paper invoices from a certain date. This is a business policy decision and needs to be backed by your finance leadership.
"What if something goes wrong?" Give them a real person to call. An onboarding contact who responds quickly to questions in the first few weeks eliminates most of the anxiety.
Running a pilot before a full rollout
If you have more than 50 suppliers to onboard, run a pilot with 5 to 10 before communicating to everyone. Pick a mix: one large PEPPOL-enabled supplier, one medium supplier using the web portal, one small supplier. Resolve the problems that come up — wrong field mappings, validation errors, confusion about the PO reference format — before they multiply across the full supplier base.
The pilot also gives you something concrete to show to other suppliers: "We have already onboarded Lieferant AG and the process took about three days." Real examples reduce resistance more than any specification document.
Tracking progress
Keep a simple spreadsheet or tracker: supplier name, tier, onboarding status, target date, and any blockers. Review it weekly. Suppliers who are overdue and have not responded to follow-up usually need a phone call rather than another email.
Most of the onboarding work happens in the first two months after you send the initial communication. After that, the pace slows but does not stop — new suppliers come on board constantly. Build the onboarding process into your vendor setup workflow so new suppliers know from day one what format you expect.
For the supplier's side of the same question — what you need to do to send invoices electronically — the guide to getting started with eBill as a Swiss SME and the PEPPOL first invoice guide are useful references to share.