24 July 2017
So it is import of service and you are required to pay tax under reverse charge.
Other view which is also possible is that Facebook Ireland is providing OIDAR (Online Information and Database Access or retrieval) Services and hence facebook ireland is required to take mandatory registration under GST.
But to be on safer side since Facebook Ireland is issuing invoice mentioning Ireland VAT so in order to avoid any complications it is advisable to treat it as import of service and pay tax under reverse charge and later on take credit of same..