T2K (Tokai to Kamioka) is a long-baseline neutrino oscillation experiment located in Japan. One of the most challenging tasks of T2K is to determine whether CP is violated in the lepton sector. By utilizing the near detector (ND280) data, T2K can constrain neutrino interaction and flux uncertainties by fitting a parametrised model to data. This allows for a significant reduction of the systematic uncertainties in neutrino oscillation analyses. This year T2K oscillation analysis brought many improvements to the cross-section model including, expanded treatment of shell structure in Spectral Function model, 2p2h pair uncertainties, updated removal energy, nucleon FSI. Also the flux systematic has been updated thanks to use the NA61/SHINE 2010 replica target data. To better constrain the new model, the ND fit introduced new samples using proton as well as photon tags, on top of the muon and pion information that T2K used so far. T2K uses two different methods to constrain flux and cross section at ND280, one of which uses Markov Chain Monte Carlo and will be discussed in this poster. The poster includes posterior distributions for selected cross-section parameters, impact of new samples as well as prior and posterior predictive distribution for chosen samples.