Event order and formula
Assume accrual on opening balance, then movement. With opening B, rate i, deposit C and withdrawal W, next balance is B × (1 + i) + C − W. It becomes the next opening balance. If movement precedes accrual, the formula changes.
Worked example
With 40,000 roubles, 1% monthly, deposit 5,000 after month one, withdraw 12,000 after month two and deposit 7,000 after month three: 40,000 + 400 + 5,000 = 45,400; 45,400 + 454 − 12,000 = 33,854; 33,854 + 338.54 + 7,000 = 41,192.54. Separate check: 40,000 × 1.01³ + 5,000 × 1.01² − 12,000 × 1.01 + 7,000 = 41,192.54.
Contributions versus income
Initial money plus deposits is 52,000; after the 12,000 withdrawal, net contribution is 40,000. The 1,192.54 difference is accrual income in this model. A final balance is not automatically income; return depends on amount and dates.
Table and controls
Track date, opening balance, rate, accrual, deposit, withdrawal and closing balance. With actual days, use the contract’s convention and see the [capitalization calendar](/guides/capitalization-calendar/). Transfers between family accounts are not new capital. At zero rates, balance must equal opening amount plus deposits minus withdrawals.
Finding a missing operation
Compare deposits, withdrawals and accruals separately with the statement. An outflow mismatch suggests sign or date; an accrual mismatch suggests base or event order. Use transfer identifiers for internal flows. See [simple and compound interest](/guides/simple-and-compound-interest/).