Oporezivanje je jedan od najmoćnijih instrumenata fiskalne politike koji ima značajne posljedice na ponudu i potražnju, utječe na ekonomski rast i investicije kao i na konkurentnost poduzeća. Također, utječe na poticaj poduzećima da ostanu u nekoj zemlji ili premjeste svoje poslovanje drugdje. Stoga je osmišljavanje optimalne porezne politike od presudnog značaja za svaku vladu. U ovom radu razmatra se problem određivanja optimalne porezne politike za jedno homogeno dobro koje proizvode dva konkurentska poduzeća smještena u dvije različite zemlje. Svako poduzeće ima jedan proizvodni pogon koji je smješten u zemlji iz koje poduzeće dolazi, dok se proizvod prodaje u obje zemlje. Države imaju različite porezne sustave. Ako poduzeće prodaje proizvod na stranom tržištu, uz trošak proizvodnje ima i trošak izvoza koji se sastoji od troškova prijevoza i troškova carine. Problem se modelira kao problem programiranja s dva sljedbenika, pri čemu vođa (vlada) maksimizira porezni prihod dok sljedbenici (poduzeća) maksimiziraju svoje funkcije dobiti. Uz to što se formulira novi model koji do sada nije poznat u postojećoj literaturi, u radu se izvodi optimalna razina poreza i pripadni iznos poreznog prihoda, izvode se optimalne razine proizvodnje i izvoza poduzeća, razmatraju se svojstva funkcije dobiti i utjecaj povećanja poreza na optimalne količine i funkcije prihoda i dobiti poduzeća te se pokazuje kako se teret poreza raspodjeljuje između proizvođača i potrošača. Model se ilustrira numeričkim primjerom. Taxation is one of the most powerful instruments of fiscal policy, having important implications on supply and demand, affecting economic growth and investments as well as the competitiveness of companies operating under a given tax policy. It also affects a company’s incentive to stay or to move its operations elsewhere. Therefore, designing the optimal tax policy is of crucial importance for any government. This study considers the problem of determining optimal tax policy for a single homogeneous commodity produced by two competing companies located in two different countries. Each company has one manufacturing facility located in its country of origin, while the product is sold in both countries. Countries have different tax systems. If a company sells the product on a foreign market, in addition to the cost of production there is also an export cost, which consists of transportation cost and duty cost. The problem is modelled as a bilevel programming problem with two followers, where the leader (the government) maximizes the tax revenue, whereas followers (companies) maximize their profit functions. In addition to formulating a new model that is not known in the existing literature so far, the paper derives the optimal tax level and the corresponding maximum amount of tax revenue, as well as the optimal production and export levels for the companies. It discusses the properties of the profit function and the impact of increasing taxes on optimal quantities and revenue and profit functions of the companies. Finally, it shows how the burden of tax is divided between producers and consumers. The model is illustrated by numerical example.