Key legal question
Whether the reconsidered pension had to be recalculated back to the original pension start date or only from discovery of the error.
Extracted holding
The correction was based on an IV-specific error, so retroactive adjustment applied only from 1 September 2013, when the error was discovered.
Extracted reasoning
The mistaken assessment concerned when the material conditions for the pension were met, not merely the implementation of an already determined entitlement; therefore Art. 88bis Abs. 1 lit. c IVV applied rather than AHV-analogous retroactivity rules.