Inter-frequency null tests of CMB TE and EE power spectra. Each sub-panel shows the differences between two foreground-cleaned cross-spectra at different frequencies (horizontal minus vertical). We show the full spectra comparisons here, even though the likelihood discards some of these data (according to the multipole range). The two lines in each panel correspond to the 2015 data and nuisance model (purple) and the 2018 one (orange); for each case, foreground and nuisance cleaning is performed at the spectrum level, as is done for the likelihood, using the best-fit nuisance parameters from the baseline fit for each release. The PTE values quoted in each sub-panel correspond to the 2018 data (and nuisance model) for the full range presented in the plot and with Δℓ = 100 flat binning. There is impressive improvement in the 2015–2018 agreement in the inter-frequency spectra, in particular in TE, due in large part to the beam-leakage corrections.