MS_UNAVAILABLE VIES error: what it means and what to do

Retried by AvatcadoAvailability error
By Remco from Avatcado

MS_UNAVAILABLE means VIES could not get an answer from the tax authority of the member state you asked about. The VAT number was not checked, so treat the result as unknown, never as invalid. Retry with backoff, and keep the order or signup pending until a check succeeds.

The application at the Member State is not replying or not available. Please refer to the Technical Information page to check the status of the requested Member State, try again later

VIES checkVatService WSDL (fault list)

What it means

VIES holds no central database of VAT numbers. It forwards each check to the database of the member state that issued the number, and MS_UNAVAILABLE is the fault it returns when the application at that member state is not replying or not available. No national database answered the check.

What causes it

The national system behind VIES is down or not replying. The VIES FAQ says parts of the system may be unavailable at certain times because member states back up their databases, and it lists regular windows for some countries, such as Germany ("Unavailable daily from 11:00 PM to 01:30 AM") and Italy ("Unavailable every Monday from 06:00 AM for 30 to 60 minutes").

How to handle it

  • Treat the result as unknown, never as invalid, and do not show the customer a "VAT number invalid" message: the fault says nothing about the number.
  • Check the member state's status on the VIES technical information page, or call GET /check-status on the REST API, which lists every country as Available, Unavailable or Monitoring Disabled.
  • Retry with exponential backoff and a cap on the number of attempts, then queue the check and run it again later.
  • Tell the user that the VAT check for that country is temporarily unavailable, and keep the order or signup pending until a check succeeds.
  • A fault response carries no consultation number (requestIdentifier). If you keep one as evidence of the check, run the check again once the member state answers.

What Avatcado does when VIES returns MS_UNAVAILABLE

Avatcado retries MS_UNAVAILABLE inside the same request, with a short pause and random jitter between attempts.

If VIES still has no answer, Avatcado asks the country's national tax register on the Pro and Business plans, for the 10 EU countries that have one (listed on the coverage page), and on every plan it falls back to the most recent stored result for that number. When neither can answer, the API returns a 503 with the code upstream_member_state_unavailable, and the call does not count against your quota. A check that ends in an availability error is never stored as an answer. A request that carries requester_vat_number skips both fallbacks by default, because a consultation number has to come from a completed VIES check.

How often Avatcado sees MS_UNAVAILABLE

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, and rates count each request's first call to VIES. 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%.

13.8% / of requests with a VIES availability error
319.7 / per 10,000 first calls to VIES
0.3% / answered after a retry
November 14, 2026 / last seen
  • Answered after a retry: of the requests that hit MS_UNAVAILABLE at least once, the share that still got a valid or invalid verdict from VIES later in the same request. A request that ended on another VIES error is not counted.

Where it happens

Countries with at least 5 requests that hit MS_UNAVAILABLE, up to 8, ranked by their share of those requests. The last column is the country's own rate per 100 first calls to VIES.

CountryShare of MS_UNAVAILABLE requestsPer 100 first calls
Germany49.8%9.4%
Poland13%7.6%
Sweden11.3%2.9%
Denmark9.1%6.3%
Portugal6.7%1.4%
Belgium2.7%1.9%
France2.7%0.3%
Finland1.8%2.2%

Week by week

MS_UNAVAILABLE per 100 first calls to VIES in each of the last 13 weeks.

Frequently asked questions

Does MS_UNAVAILABLE mean the VAT number is invalid?

No. MS_UNAVAILABLE means VIES could not reach the member state's database, so no check took place. VIES reports a number as invalid only after the member state's database has been asked and the number is not recorded there. Treat the result as unknown and check the number again once the member state answers.

Where can I see whether a member state is unavailable in VIES right now?

VIES shows the status of each member state on its technical information page, and the REST API has a check-status endpoint that lists every country as Available, Unavailable or Monitoring Disabled. Avatcado's VIES uptime page adds the failure rate per country measured on its own production traffic.

Keep reading

Sources

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