A VAT check is true for one instant: the retention question is which moments you re-run it

The artifact that matters is not the yes or no. It is a row: the exact string you sent, the source that answered, the answer, and the time the query ran ^[1]. Strip the timestamp and the row cannot do its only job, because the check that supports a given invoice is the one reflecting the customer's status around the time of that supply ^[7].

Two different things also get filed under the same label, and should not be. A string can match a country's pattern perfectly and still not be an active VAT ID; only a live check against VIES or a national source confirms registration ^[2]. A record that says "validated" without recording which of those two happened is not evidence you would want to lean on.

Onboarding earns its place for a reason that has nothing to do with tax law: it catches typos and plainly wrong numbers while the customer can still fix them, which is cheaper than finding a bad number on an invoice already issued, and it fixes a baseline date ^[4]. That is a support-cost argument. Keeping it separate from the compliance argument is what tells you how hard each check should fail.

The same stored row then gets used for two different legal purposes. For cross-border B2B services, the place of supply is generally where the customer belongs under Article 44 of Directive 2006/112/EC, liability shifts to the customer under the reverse charge in Article 196, and the customer's VAT ID supports applying that treatment ^[5]. For goods, per the same guide, the ID sits alongside proof of intra-Community transport and correct invoicing, and does not secure zero-rating on its own ^[12].

Nothing arrives to tell you a registration has gone ^[3], and a number valid at signup can be cancelled the following week ^[14]. So the recheck interval, and nothing else, sets how long a dead number can sit in billing looking alive: quarterly checks leave roughly ninety days, an annual sweep leaves up to a year ^[1]. Choosing the cadence is choosing the length of that blind spot; there is no arrangement in which the registration reports its own death.

Two limits on the material. The scope is the EU-27 plus XI for Northern Ireland, which is the area VIES covers, and the author presents it as general information about EU VAT rather than tax advice ^[6][9]. And the guide sets out four moments plus what to store at each ^[10]; the version published on dev.to develops three of them, onboarding, the invoice, and the periodic recheck, before it breaks off mid-sentence ^[2]. Anyone building a retention schedule from this text is building it with one trigger and most of the storage guidance still missing.