In the event that a Member State sets a limitation period after which the right of a taxable person with a definitively irrecoverable debt to a reduction of the taxable amount lapses, according to the ECJ, on the basis of Article 90 of the VAT Directive (in conjunction with the principle of fiscal neutrality and the principle of effectiveness) does not start this limitation period at the time when the payment obligation should originally have been fulfilled, but at the time when the debt has become definitively irrecoverable.
Source BTW jurisprudentie
See also
