Search for lepton number and flavour violation in $K^+$ and $\pi^0$ decays

The NA62 experiment at CERN collected a large sample of charged kaon decays into the final states with multiple charged particles in 2016-2018. This sample provides the sensitivities to rare decays with branching ratios as low as $10^{-11}$. The results from the searches for lepton flavour/number violating decays of the charged kaon and the neutral pion to the final states containing a lepton pair based on this data set are presented.