I think this is it.
(IV) in the case of a dwelling to which the European Union (Energy Performance of Buildings) Regulations 2012 (S.I. No. 243 of 2012) apply and that has a BER of D1 or lower, the BER (within the meaning of those Regulations) being improved by not less than 3 building energy ratings;
or
(V) in the case of a dwelling to which the European Union (Energy Performance of Buildings) Regulations 2012 (S.I. No. 243 of 2012) apply and that has a BER of C3 or higher, the BER (within the meaning of those Regulations) being improved by not less than 2 building energy ratings,