VIES error codes and what to do about each one

Avatcado treats 6 VIES errors as availability errors, meaning VIES could not complete the check. None of them says the VAT number is invalid. Each page below explains one error, what to do about it, and how often it shows up in Avatcado's own production traffic.

MS_UNAVAILABLE

Retried

The member state's own system is not replying or not available.

13.8% of requests with an availability error, last 90 days

Cause and fix →

MS_MAX_CONCURRENT_REQ

Retried

Too many requests are open towards one member state at the same time.

86.6% of requests with an availability error, last 90 days

Cause and fix →

TIMEOUT

Retried

VIES did not receive a reply within its allocated time.

3.5% of requests with an availability error, last 90 days

Cause and fix →

SERVICE_UNAVAILABLE

Retried

VIES hit an error at the network or web application level.

Cause and fix →

GLOBAL_MAX_CONCURRENT_REQ

Not retried

VIES as a whole reached its maximum number of concurrent requests.

Cause and fix →

VOW-ERR-11

Retried

A REST API error reading "A mandatory field is missing". On 2026-09-04 Avatcado got it on complete requests while VIES listed one of the member states as unavailable.

Cause and fix →

Other faults a VIES client can meet

These faults are not availability errors, so they have no page of their own. Each meaning comes from the source named beside it.

CodeMeaningSource
INVALID_INPUTThe country code in the request is invalid, or the VAT number is empty.VIES checkVatService WSDL (fault list)
INVALID_REQUESTER_INFOVIES rejected the requester details sent with the check. Its message reads "Invalid requester VAT number".Error messages shown by VIES on-the-web (English); VIES checkVatTestService WSDL (test numbers per fault)
MS_MAX_CONCURRENT_REQ_TIMEThe concurrency limit for the member state was reached in the current timeslot, so the request was not processed.Error messages shown by VIES on-the-web (English); VIES checkVatTestService WSDL (test numbers per fault)
IP_BLOCKEDYour IP address is blocked. The VIES FAQ says an IP address is blocked when its requests are recognised as abusive use, and to contact TAXUD-VIESWEB if you think the block is wrong.Error messages shown by VIES on-the-web (English); VIES FAQ, including member state availability windows
VAT_BLOCKEDThe VAT number is currently blocked. VIES asks you to contact TAXUD-VIESWEB@ec.europa.eu.Error messages shown by VIES on-the-web (English); VIES checkVatTestService WSDL (test numbers per fault)
NETWORK_ERRORAvatcado's own label, not a VIES code. Avatcado records it for a VIES call that failed without a VIES answer, such as a refused connection or an HTTP error with no readable body.Avatcado's VIES client

Where the figures come from

The figures on each page are read from the VIES calls Avatcado made for customer API keys in the last 90 days, with test keys and the demo checker left out. Each request counts once, however often Avatcado retried it: shares count requests, rates count each request's first call to VIES, and the pages publish shares and rates only. A request can meet more than one of these errors while it is retried, so the shares across codes can add up to more than 100%. A code seen in fewer than 30 requests in that window shows no figures. The VIES uptime page has the failure rate per member state, the coverage page lists the national registers Avatcado consults on the Pro and Business plans when VIES cannot answer, and the VIES downtime guide covers retry and fallback design in your own code.

Sources

Validate VAT numbers with the retries and fallback built in.

National register fallback on Pro and Business. Free tier: 500 validations a month.