The mixing of three neutrino flavours is parameterised by the unitary
PMNS matrix. If there are more than three neutrino flavours, effective $3\times 3$ neutrino mixing
matrix will be non-unitary. In this paper, we have analysed the
latest T2K and NO$\nu$A data with the hypothesis of non-unitary mixing matrix.
Present results from NO$\nu$A and T2K collaboration have tension between them as NO$\nu$A disfavours T2K
best-fit point at $1\, \sigma$ confidence level and vice versa. In this paper we have shown that latest data from both the
experiments disfavour unitary $3\times 3$ mixing at $60\%$ C.L. The combined analysis disfavours unitary mixing
at $1\, \sigma$ C.L. Moreover, the tension between two experiments can also be reduced with the non-unitary approach.