This chapter presents finite blocklength analyses for point-to-point mismatched channel coding, where optimal codes for data transmission over an AWGN channel are used to transmit a message over an additive arbitrary noise channel. Two kinds of code books, including i.i.d. Gaussian codebooks and spherical codebooks, are studied and compared in terms of low-latency communication performance. A take-home message is that although both i.i.d. Gaussian and spherical codebooks achieve the same infinite latency performance, the low-latency performance of spherical codebooks is significantly better. The readers can learn coding schemes for mismatched data transmission and its low-latency theoretical performance.