I think that if the OP were an accrual basis taxpayer they would already know how to handle this situation, since accrual-basis accounting is opt-in for individ

I think that if the OP were an accrual basis taxpayer they would already know how to handle this situation, since accrual-basis accounting is opt-in for individuals and S-corporations. Note to other reply: estimated tax payments are made during the year. While you can net out expenses, if income is distributed unequally during the year this can result in penalties/interest if you underpay in one quarter based on the liability as calculated after the year ends (to complicate things, there are multiple ways to estimate tax payments during the year to account for these situations).