VIES ERROR: “The maximum number of concurrent requests has been reached” (MS_MAX_CONCURRENT_REQ)
for French (FR) EU VAT numbers – workaround using new asynchronous function getVIESDataAsync
Dear customers,
Due to the very large number of emails and phone calls sent to us, we would like to inform you that for about a week we have been noticing a very large number of errors returned from the VAT Information and Exchange System (VIES) for requests sent with French EU VAT numbers (with the “FR” prefix).
All errors returned concern the limit related to reaching the maximum possible throughput of the French tax system: The maximum number of concurrent requests has been reached (MS_MAX_CONCURRENT_REQ).
Due to the numerous questions, we would like to emphasize very strongly that this is not an error related to our API (viesapi.eu), because apart from limiting the number of requests purchased within a given plan, we do not apply any limits on the number of requests sent via our system.
The same situation occurred in 2023, but it concerned the German tax system (DE), which was also practically unavailable for 2 months due to very high traffic and a large number of requests. You can learn more about that situation in our article, which we also published at that time to explain the situation: Serious problems (MS_MAX_CONCURRENT_REQ error) with verifying companies from Germany (starting with DE) in VIES.
We do not note similar errors in the case of other tax systems of EU Member States. Currently, there are problems only with the verification of contractors from France (with the FR prefix).
You can read more about this problem and others related to the availability of VIES in the article on our blog: https://viesapi.eu/vies-unavailability-of-vat-information-exchange-system/
Please send all emails directly to the official technical support address of the VIES system: TAXUD-VIESWEB@ec.europa.eu
We hope that the large number of reports about the unavailability of VIES and the inability to verify contractors from France (FR) will have a positive impact on the quick resolution of the problem.
Workaround: At the moment, the only workaround we see that works is to send requests (EU VAT number with FR prexif) outside peak hours, i.e. 6:00 p.m. – 8:00 a.m.
[Update 03/18/2025]
1. Workaround – We have provided new asynchronous functions for the REST API and programming libraries that allow for batch querying of VIES and at the same time bypass the error “The maximum number of concurrent requests has been reached” (MS_MAX_CONCURRENT_REQ). We encourage you to test them.
2. After about a month of waiting, we received an official response from VIES Support Team to our next letter regarding errors and lack of stability of the VIES System. Below is the full content of the received e-mail:
Dear User,
Sincere apologies for the short delay in responding to your issue.
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 https://ec.europa.eu/taxation_customs/vies/#/help).
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 address both the VoW overall as well as each Member State separately and for each type of validation request namely, WEB Interactive (Manual – INT) as well as SOAP (API), REST (API) and/or BATCH services.
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 validations (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 case you were mostly attempting to validate German (DE), French (FR) and/or Czech Republic’s (CZ) VAT numbers via the VoW, according to our investigation, indeed, all three national VIES components indicated have been facing temporary latency issues that also cause the “MAX_Concurrent” error responses that you receive.
For your information we are aware of the issues. The competent departments of the three National Tax Administrations are working towards a resolution the soonest possible.
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: https://ec.europa.eu/taxation_customs/vies/#/help
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 (https://ec.europa.eu/taxation_customs/vies/#/self-monitoring)
Again, we suggest that each time such an issue occurs, we suggest that you resubmit your request(s) sometime later and/or allow sometime between validations (few seconds).
Alternatively, up until resolution of this temporary issue explained above, you may also use the VoW “BATCH” validation service of the VoW (https://ec.europa.eu/taxation_customs/vies/#/batch-validation). More information may be found here: https://ec.europa.eu/taxation_customs/vies/#/technical-information
Sincere apologies for the inconvenience.
Please contact us if you have any further issues.
Kind Regards
ITSM VIES/Web Technical Support Team
VIESAPI Team
