What is the procedure for challenging a decision to refuse a VAT refund claim?

The channels for appealing against a refusal decision are set out in the document notifying the decision.

Out-of-court procedure

For an out-of-court settlement, contact the Mediator at the Directorate for Residents Abroad and General Services (DRESG), whose contact details are as follows:

Le Conciliateur fiscal de la Direction des Résidents à l’Etranger et des Services Généraux
10, rue du Centre
TSA 70025
93465 Noisy-le-Grand Cedex

[email protected]

You must send a copy of the decision with your referral, and all information and/or documents, especially those that provide evidence of which the department was unaware when it made its initial decision.

Source impots.gouv.fr