Separate accrual from crediting
Accrual is the calculation of income for an interval. Crediting is recording the amount in the account. Capitalization is including credited interest in the base for later calculation. A learning table should show these actions separately even when the contract sets them on one date.
Income may be calculated daily but added to the deposit monthly. Daily calculation does not prove daily capitalization, and payment at month-end does not prove that the bank used an equal fraction of a year. Find the definitions in the product terms.
Record the start and end of every interval and the rule for boundary dates. Excluding the start and including the end is only an announced assumption; the real rule comes from the contract.
Two months with different income
Assume a hypothetical 100,000 roubles, a 12% rate and a 365-day year. The learning intervals run from January 1 to February 1 and from February 1 to March 1, 2027. Excluding the start and including the end gives 31 and 28 days.
The first interval earns 100,000 × 0.12 × 31 / 365 = 1,019.18 roubles after rounding for display. If it is capitalized while the exact unrounded amount is carried forward, the second-period base becomes 101,019.178… roubles. The next 28 days earn approximately 929.93 roubles.
Without capitalization, the second interest amount on the original principal would be about 920.55 roubles. The difference reflects both duration and base. The numbers are educational; intermediate-rounding rules can change the final kopecks.
Top-ups, weekends and changing rates
A new contribution splits the period if it starts earning from a particular date. Before that date the old base applies; after it, the new base applies. Add an event row rather than spreading the contribution over a whole month.
A non-working-day adjustment cannot be modeled by habit. Determine whether only technical crediting moves or whether the date on which interest enters the base also moves. If the document is unclear, record the uncertainty and ask for clarification.
If the rate changes on the capitalization date, record the order: which interval used the old rate and from when the new rate applies.
Check the table instead of trusting the total cell
Minimum columns are period boundaries, number of days, annual basis, balance, rate, accrual, capitalization and separate payment. Check several rows independently and reconcile balance transitions. Total accrual should match payments plus capitalized income, subject to the stated rounding rule.
Keep exact model values separate from rounded display values. If the document requires rounding each payment, reproduce that rule. Do not adjust rates to match another calculator before comparing calendars and assumptions.