MS_MAX_CONCURRENT_REQ Error for Germany (DE) EU VAT numbers

Dear Customers,

Due to the large number of reports sent by you regarding the inability to verify contractors in the VAT Information and Exchange System (VIES), who use the German EU VAT number (DE), we would like to present you the official response of the VIES technical support team.

Below is our question:

We have noticed that for a long time, when querying via API, there have been very serious problems with obtaining information on the VAT taxpayer status for contractors from Germany (MS_MAX_CONCURRENT_REQ error).

Can you improve the quality of API responses for queries regarding German contractors (containing the “DE” prefix)?

We would like to thank you very much on behalf of our clients who would like to be able to efficiently verify contractors from Germany.

and full answer:

Dear User,

Thank you for contacting us the VIES/Web team.

Taking this opportunity, we would like to inform you about some basic elements of the VIES-on-the-Web (VoW) service.

The VoW application (indeed the whole VIES system) operates on the basis of real-time exchanges. Each validation request that you submit to VoW is forwarded in real-time to the national VIES system of the relevant administration.

This national system performs the validation against its national database and provides the result back to VoW, which displays it to you. If the national part of VIES is not available, then you will get a corresponding answer (you may also refer to ).

The VIES web system is designed for single requests. Since there is no central vies web database the reply from the corresponding national database would vary from 1 to several seconds.

However, there is a limitation on the concurrent requests handled by VoW. There is a maximum number of concurrent requests the system can handle. If the system receives a new request and the maximum number of concurrent requests is reached, the request is rejected.

The maximum number of concurrent requests is not linked to a specific IP. It is a global count across all users. In addition, the MAX Concurrent limitations addresses both the VoW overall as well as each Member State separately and for each type of validation request namely, Manual (INT), SOAP (API), REST (API) as well as BATCH.

On request though from some National Administrations, we unfortunately cannot disclose the exact level of the thresholds in VoW.

Each time there is a similar issue, our technical team performs an analysis in close contact with all involved parties in order to identify the root cause that creates these temporarily unavailability issues.

Mind you that this unavailability usually does not last too long.

Each time such an issue occurs, we suggest that you resubmit your request(s) allowing sometime between validation requests (few seconds or minutes).

In addition, please consider that the VIES-on-the-web service that you use to submit requests, consists of a central component and 28 national components (one for each Member State).

When you make a validation request, the central component of the service, forwards it in real-time to the national VIES of the relevant tax administration.

Since the Web application (indeed the whole VIES system) operates on the basis of real-time exchanges all components of the VIES (the central and 28 national) must be available in order to execute a validation.

The Commission is responsible for the central component of the service and the Member States for the national components of the VIES.

When you face an unavailability of the service, this may be due to issues of one of the VIES components.

Each national VAT administration maintains its own database and is legally responsible to keep its national system updated and available.

The Commission is closely monitoring the performance of the national systems and is acting with national administrations, in order to ensure the highest availability of the web service.

Despite our efforts, there might be times when certain national services are unavailable, or the response time is slow.

As may already know, unavailability of the national system does not last for very long.

In your case, the German (DE) national VIES component has been facing temporary unavailability issues for quite a while.

For your information we are aware of the issue. The competent department of the German National Tax Administration is working towards a resolution. The issue is under investigation by all competent teams involved.

Please also consider that there are scheduled unavailability shifts of the service (e.g., for maintenance reasons, or update of the databases).

For any scheduled unavailability shifts, you may consult the HELP page pf the VoW:

Moreover, for a live monitoring of all 28 EU National VIES components, you may consult the “MSA / XI Availability” section at the “Self-Monitoring” page of the VoW (

Each time such an issue occurs, we suggest that you resubmit your request sometime later.

Apologies for any inconvenience.

Please contact us if you have any further issues.

Kind Regards

ITSM VIES/Web Technical Support Team

“ITSM3 TES is a contracted support partner for the IT Service Management of the European Commission. This e-mail is a reply to your message sent to the e-mail. Answers provided by the contactor are on behalf and according to policy guidelines of DG TAXUD, but not binding for the European Commission.”


At the moment, the only workaround we see that works is to send requests (EU VAT number starting with DE) outside peak hours, i.e. 6:00 p.m. – 8:00 a.m.