VATrelay → VIES errors

`MS_MAX_CONCURRENT_REQ`

What it means

The member state's VIES backend is refusing requests because too many are already in flight — across all VIES users worldwide, not just yours.

Whose fault is it

Not your code. Not your IP. Not your rate limit.

What to do

Retry with backoff, and cache aggressively. We measure the French backend answering roughly one request in six, so retrying alone will not save a checkout flow. The only robust fix is to serve a cached answer and degrade explicitly.

Live VIES availability, measured

Member state	Now	24 h	Last error
FR	down	33.0%	MS_MAX_CONCURRENT_REQ
DE	up	79.0%	—
BE	up	97.0%	—
ES	up	100.0%	—
IT	up	100.0%	—
NL	up	100.0%	—
PL	up	100.0%	—
PT	up	100.0%	—

We query each member state's real backend every 10 minutes with a live VAT number. The Commission's own status endpoint reports Available for member states that are in fact refusing most requests — only a real call tells the truth. This data is free and needs no account: GET /v1/uptime.

Stop handling this yourself

VATrelay absorbs every error on this page. When VIES is silent we serve the last known answer, flagged stale with its original timestamp, or the offline structural verdict — always HTTP 200, always a usable body. We never invent a validity verdict.