In Russia, Kazakhstan and Belarus
Russia
The address is lkfl2.nalog.ru, and there is a mobile app. You can log in through Gosuslugi, with the login and password from the tax office or with an electronic signature. Users of the account are not sent paper tax payment notices.
Kazakhstan
In Kazakhstan it is the «Taxpayer's Cabinet» («Кабинет налогоплательщика») of the State Revenue Committee; some tax services are also available on eGov.
Belarus
In Belarus it is the payer's personal account on the portal of the Ministry of Taxes and Duties (МНС): it shows the taxes charged, and you can file a return and pay tax.
Sources: Taxpayer's personal account of the Federal Tax Service («Личный кабинет налогоплательщика ФНС»), Federal Tax Service of Russia («ФНС России»)