Corporate income tax is one of the important taxes that provide revenues to the state budget. Article contains a comparison between Latvian and Lithuanian existing legislation relating to corporate income tax, studied differences between the tax rates, tax base, tax period and taxpayers. Were described differences that are related to the advance payment calculation, as well as created an example that shows how advance payments are calculated in Latvian and Lithuanian companies. As a result, it was found that there are several common features in the Latvian and Lithuanian legislation, with regard to corporate income tax, for example, the tax payers, taxation period, tax rate, the taxable amount. But there are several differences, such as the nuances of rates for non-residents, depending on the type of revenue, advance payment deadlines and other particularities of the calculation of the advance payments. Also differ corporate income tax payment deadlines. It was concluded that making advance payments in Lithuanian enterprises is more profitable, because it was calculated that at the same conditions, the amount of advances in Lithuania is lower than in Latvia.