This study investigated the effect of tax planning on firm value of selected deposit money bank in Nigeria. It examines the effective tax rate and book-tax difference effect on the firm value. This study adopted the ex-post facto research design, population of 15 listed deposit money bank in Nigeria, sample size of 11 were selected through the use of the two-point filter. One, a company must be listed on or before January 2015 and be continuously listed until December 2024, as this study covers 2015 - 2014. Secondly, the company should not have been taken over or absorbed by any other company during the study. It employs multiple regression, analysed through STATA 13, and panels collected standard errors was adopted as suitable for the panel data. The result reveals that book-tax difference has a negative and significant effect on firm value, while effective tax rate is insignificant. This study concludes that effective tax rate has no significant effect on firm value, while book-tax difference has negative effect. This study recommends that the management of the deposit money banks should reduce aggressive book-tax difference development and emphasise on sustainable effective tax rate optimisation by taking legitimate deductions.