What exactly does the contract specify?
Under Article 838 of the Civil Code of the Russian Federation, the interest amount is determined by the bank-deposit contract. Therefore, “12% per year” does not describe the whole product: the term, the timing of interest accrual and payment, whether deposits or withdrawals are allowed, early-return terms and other restrictions matter.
Article 839 establishes the general rule that interest accrues from the day after the money arrives at the bank through and including the day of return. A particular contract may set additional payment and capitalization terms.
Why 12% per year is not 12% for three months
For a simple scenario without capitalization, the annual rate can be allocated across calendar days. The Bank of Russia uses the same principle in educational materials: simple interest depends on the principal, annual rate and number of accrual days.
For example, placing RUB 100,000 at 12% per year for 90 days in an ordinary 365-day year gives approximately RUB 2,959 of interest under the simplified calculation: `100,000 × 12% × 90 / 365 ≈ 2,959`.
This is not a bank promise or a universal formula for every deposit. It is a transparent baseline scenario that shows the scale.
What changes with capitalization?
With capitalization, accrued interest is added to the amount on which later interest is calculated. Two deposits with the same nominal annual rate can therefore produce different totals when capitalization frequency and other terms differ.
That is why the calendar tool and the periodic capitalization model are separate. In the periodic model, equal months are a calculation assumption, not a copy of a bank contract. Real contracts may use different interest-period dates and accrual rules.
Why look beyond the advertised rate?
For comparison, separate the nominal rate from the stated scenario: how much is deposited, for how long, which conditions must be met and how much will be received under those conditions. The rate alone does not replace reading the contract and checking its restrictions.
The simple calculation does not replace the terms of a particular product or special regulatory indicators. It shows which assumptions are included and what the model omits. The historical note about the effective rate in the glossary is marked as historical; the 2026 methodology is not confirmed there.
What does the calendar scenario do?
The Bank Portal calculator uses only a fixed amount and fixed annual rate between two calendar dates. The opening day is excluded and the ending date is included. Each day uses 365 or 366 according to the calendar year.
It does **not** account for capitalization, additional deposits, partial withdrawals, taxes, bonuses, stepped rates, a minimum balance or early termination.
Its purpose is therefore not to choose a deposit, but to provide a reproducible control point for reading the terms.