VAT.law (beta)
The VAT  handbook

- Supply of availability to provide consultancy services: charge at end of each period for which service available 

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"[49] Thus, a service such as that at issue in the main proceedings, which in essence entails being permanently available to the customer in order to provide it with consulting services and which is remunerated by means of fixed sums paid periodically, must be regarded as being supplied in the period to which the payment relates, whether or not the service provider has actually provided advice to its customer during that period.

[50] It is at the end of each period to which the payments relate that the supply must be regarded as having been completed for the purposes of Article 64(1) of the VAT Directive. Since the chargeable event and the chargeability of the tax depend on the moment when the service is supplied, in accordance with Article 63 of that directive, it follows that it is also at the end of each of those periods that that event and that chargeability occur." (Asparuhovo Lake Investment Company C-463/14)

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