The Modigliani–Miller theory, discussed in Chapter 5 , has a lot of limitations. One of the most important and serious assumptions of the Modigliani–Miller theory is that all financial flows as well as all companies are perpetuity. This limitation was lift out by Brusov–Filatova–Orekhova in 2008 (Filatova et al., Bull FU 48:68–77, 2008), who have created BFO theory–modern theory of capital cost and capital structure for companies of arbitrary age (Brusov et al., Modern corporate finance and investments, monograph, Knorus Publishing House, Moscow, 2018a; Brusov et al., Modern corporate finance, investments, taxation and ratings. Springer Nature Publishing, Switzerland, 571 p. monograph, 2018; Brusov et al., J Rev Glob Econ 7:37–62 SCOPUS. DOI: https://doi.org/10.6000/1929-7092.2016.07.05 , 2018c, Brusov et al., SCOPUS, 2018d, Brusov et al., J Rev Glob Econ 7:63–87. SCOPUS. DOI: https://doi.org/10.6000/1929-7092.2016.07.06 , 2018e, 2018f, 2018g, Brusov et al., J Rev Glob Econ 8:437–446, 2019, Brusov et al., J Rev Glob Econ 9:257–266, 2020; Filatova et al., Bull FU 48:68–77, 2008; Filatova et al., J Rev Glob Econ 7:645–661, SCOPUS. DOI: https://doi.org/10.6000/1929-7092.2016.07.59 , 2018b). Despite the fact that the Modigliani–Miller theory is currently a particular case of the general theory of capital cost and capital structure–Brusov–Filatova–Orekhova (BFO) theory—it is still widely used in practice. In current Chapter we discuss one more limitation of Modigliani–Miller theory: a method of tax on profit payments. Modigliani–Miller theory accounts these payments as annuity–immediate while in practice these payments are often making in advance and thus should be accounting as annuity–due. We generalize the Modigliani–Miller theory for the case of advance tax on profit payments, which is widely used in practice, and show that this leads to some important consequencies, which change seriously all the main statements by Modigliani and Miller (Brusov et al., J Rev Glob Econ 9:257–266, 2020).