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The perturbations in the electron number density during recombinationcontributes to the Cosmic Microwave Background bispectrum through second orderterms. Perturbations in the electron density can be a factor of ~5 larger thanthe baryon density fluctuations on large scales as shown in the calculations byNovosyadlyj. This raises the possibility that the contribution to bispectrumarising from perturbations in the optical depth may be non-negligible. Wecalculate this bispectrum and find it to peak for squeezed triangles and ofpeak amplitude of the order of primordial non-Gaussianity of local type withfNL of 0.05 ~ -1 depending on the l-modes being considered. This is because theshape of the bispectrum is different from the primordial one although it peaksfor squeezed configurations, similar to the local type primordialnon-Gaussianity.

Crinkles in the last scattering surface: Non-Gaussianity from inhomogeneous recombination