How to test the receiving part for Flowin?

You can set up a test receiver and test sender:

1. Register a ‘sender’ supplier with supplier-ID XXX
2. Register a ‘receiver’ supplier with supplier-ID YYY
3. Send from sender to receiver

When using webhooks, this avoids confusion with the supplier-IDs, as it will be a different ID used to send the invoice.

Keep in mind that a receiver you create could receive documents from any other sender on the test network. Those documents should never be treated as real documents.

What is the difference between integration and production? Are documents on integration actually sent to the customer?

Integration = test-network. 

For e-invoicing, integration is connected to Peppol’s test-network. It behaves the same way as production. Invoices are sent over the test-network and can be delivered to the receivers set up on that network. However, not all receivers that are on production are registered on that test-network.

We have a few test receivers you can safely send to.

Which countries can we SEND FROM?

The countries in lime highlight on this page are currently supported: 

• Belgium
• Germany
• Ireland
• Luxembourg
• the Netherlands
• Sweden

The page also lists the countries that are in scope for the coming months.

Which countries can we SEND TO?

Flowin supports sending to every country that is connected to Peppol (Europe, Canada, UK, USA, Australia, etc.). 

Receivers can choose which service provider to use for their Peppol registration (and may use a service provider that is not in their country of residence). 

See also below: How can we check if the customer is registered on Peppol?

Can we send by GLN (Global location number) endpoint?

Yes.

The EAS identifier is ‘0088’.

Read more: Peppol Documentation (check the most recent version of Peppol BIS Billing)

Can we receive on GLN (Global location number) endpoint?

This is currently not supported.

What is the difference between SchemeID 0208 and 9925 for Belgium?

Each country has its own Scheme Identifiers. For Belgium, the use of 0208 (followed by company registration number) is mandatory, while 9925 (followed by VAT number) is optional.

Therefore, it is best to use 0208.

Read more: How can we reach and/or check (non-)Belgian receivers?

How can we reach and/or check (non-)Belgian receivers?

Check with your customer: the sender should know the identifier. 

Each country has its own Scheme Identifiers. For example, in Belgium: use 0208 before the company registration number.

Frequently used identifiers in Belgium and neighboring countries:

How can we check if the customer is registered on Peppol?

You could offer this functionality in your software via the API: Peppol Customer search

There are 2 options:

• check before sending
• do a batch lookup of all the possible customers beforehand (better performance when sending batch invoices)

If you do not offer this, your customer could use the site Peppol Participant Information:

1. In the field ‘Identifier value’: enter the SchemeID followed by the identifier. For example:
   
2. Click ‘Show details’.

Note: we do not support sending to Hermes.

Can our customers still send invoices to companies that don’t use Peppol (yet)?

Yes: they can use a different delivery method such as email.

Important: in Belgium, e-invoicing will become mandatory in 2026, for transactions between companies that are subject to VAT.

Do enterprises who do self-billing also have to send via Peppol?

Yes, self-billing also falls under the e-invoicing requirements applicable from 1st January 2026. The supplier must be registered as a receiver.

At the moment, Flowin does not support self-billing, but this is planned for mid-November 2025.

Read more: Please check the latest Self-billing specification on the Peppol Documentation

What are the requirements for adding discounts to UBL invoices?

This is determined in the Peppol Documentation concerning Allowances.

Read more: Peppol Documentation (check the most recent version of Peppol BIS Billing with details on cac:AllowanceCharge)

Examples: 

Peppol BIS 3 invoice Allowance examples

UBL.BE invoice Allowance examples

What is the maximum size of a UBL?

100 MB is the maximum, including attachments.

Please check more details here: Peppol Documentation

Our customer has successfully sent an invoice but now wants to change the document. What to do?

Once an invoice is sent via Peppol, it is delivered to the receiver and the content of the document cannot be modified.

Inform your customer about the legally required steps to follow for the correction of an erroneous invoice, regardless of when the error is discovered:

1. Create a credit note to cancel (part of) the invoice and send it the same way and to the same receiver.
2. Create a new invoice with the correct details and with a new invoice number. Send it the same way and to the same receiver.

These steps need to be followed even in the event of minor textual changes.

We sent a document but the recipient claims he didn’t receive it. What can we do?

Use Transmission ID:

Once a document is successfully sent to a receiver via Peppol, the document status will indicate a ‘transmission ID’ (this is the first level of feedback, acknowledging the transfer of the document from the sender’s access point to the receiver’s access point). The sender should share this transmission ID with the receiver, so that the receiving party can check with their Peppol Access Point provider.

Check validation rules:

Some receivers have extra validation rules after accepting the document. An example is the Flemish Government who requires a correctly formatted order reference, more info can be found here:

• Website of the Flemish government
• Mercurius for the private sector

Sending failed?

If Flowin was not able to send the document to the receiver, the document status will indicate an error.

For more information about possible errors, please see the Flowin API Reference.

Do you re-send failed invoices?

No. Flowin does not re-send documents that previously failed to send.

You are advised to set up systems for failed invoices based on the errors provided. 

If a document is valid, but could not be sent due to a temporary technical problem, you can try to send the document again.

Can duplicates happen? How to stop double invoices?

Flowin doesn’t check for duplicates. 

You are advised to provide checks for this, to ensure that each document is unique and cannot be sent more than once. When receiving invoices for your customer, Flowin doesn’t check for duplicates either.

Is it possible to send other (PDF) files linked to a Peppol BIS XML without encapsulating these in the XML file?

Yes: you could add a link in the UBL in the tag ExternalReference.

You will be required to host those links yourself. They cannot point to a Flowin location.

Read more: Peppol Documentation (check the most recent version of Peppol BIS Billing with details on cac:ExternalReference)

Is it possible to send an invoice to more than one receiver at once (for example cc recipient)?

No. 

Flowin/Peppol does not facilitate sending behavior similar to CC email or BCC email. There cannot be more than one EndpointID (identifier of the receiver).

Unless the receiving access point handles this particular behavior, you will need to send the document twice.

Supplier data in document can’t be matched with data of supplier. What does this error mean?

The invoice could not be sent due to the error: ‘Value found in xxxx can't be matched with internal supplier data: xxx’

This error means, for example, that the name of the sender does not match exactly with the name that was used to create this sender on Flowin. The difference in the name could be due to a recent change or could be a typo.

Before sending documents, we check whether the name and IBAN match.

You can correct this by changing the UBL so that the UBL tag is generated correctly, or allow your customer to change the data via your software.

More info: see the UBL tags in Document verification.

MLR-IMR: What is ‘Message Level Response’? What is ‘Invoice Message Response’?

Flowin has recently launched MLR (automatic) and IMR (optional). Please see our documentation for more details on implementation.

MLR (Message Level Response) is a Peppol message that is automatically sent from the receiving service provider to the sending service provider, to indicate if the structural content of the document is correct. This is handled by the access point (Flowin) and is translated into technical status of the document.

IMR (Invoice Message Response) is a Peppol message that can be sent from the buyer (recipient of the document) to the seller (sender of the document) to indicate the business status of the document that was sent to the buyer. For example, a buyer can indicate that an invoice has been paid.

Sending IMR: This will have to be triggered by the receiving party’s software through our API.

Receiving IMR: We translate the technical process into business statuses and provide webhooks as these messages are asynchronous.

Can we put incoming invoices temporarily on hold?

Flowin does not provide such a feature. 

You can set up systems to allow for this, so that your customer can check the invoice before processing it.

Do we need to provide the inbound documents to the supplier?

Yes. 

We do not offer an alternative way to deliver the documents, such as email or FTP,... . 

Please see our documentation for more information: Peppol Inbound Documents.

How long do documents remain available for download?

All inbound and outbound documents are kept for 6 months. 

Inbound documents can be downloaded multiple times if needed.

More info about Peppol:

• General questions about Peppol (e-invoice Belgium)