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UNDERSTANDING THE DATA
Estimate interest, entered tax and fees for your own deposit terms. This is a manual calculation, not a comparison of verified bank offers.
The model uses a constant nominal annual rate and simple interest over the entered months. Net return remains unknown until all required tax and fee inputs are supplied.
Calculate the return from a rate and fees you enter. Check the terms of your own bank; this tool supplies no bank offer or current market rate.
Example: CZK 100,000 for 12 months at an assumed 3% annual rate. The model assumes 15% tax and zero fees. Edit every value as needed; these assumptions establish neither a bank offer nor your actual tax treatment.
100000 CZK · 12 months · 3 % p.a.
{
"method": "manual-simple-nominal-deposit-v1",
"basis": "user_inputs",
"input": {
"kind": "savings",
"currency": "CZK",
"principal": "100000",
"months": "12",
"annual_rate_percent": "3",
"tax_percent": "15",
"opening_fee": "0",
"monthly_fee": "0",
"closing_fee": "0"
},
"gross_interest": "3000.00",
"tax": "450.00",
"fees": "0.00",
"known_partial_fees": "0.00",
"net_interest": "2550.00",
"ending_balance": "102550.00",
"net_return_percent": "2.55",
"net_return_rounded": false,
"exact_gross_interest_cents": {
"numerator": "360000000000000",
"denominator": "1200000000"
}
}Gross interest = deposit × nominal annual rate / 100 × months / 12. Rate and principal remain constant throughout. Interest is not compounded, and the model contains no recurring deposits or withdrawals.
Gross interest rounds to two decimal places; the entered tax is calculated on that amount and rounded the same way. Fees = opening + monthly × months + closing. Net return = gross interest − tax − fees. Half a minor currency unit rounds away from zero. Fees do not reduce the interest-bearing principal during this model.
The resulting percentage covers the selected term; it is not APY. A constant rate can simplify actual savings-account terms. Check bonus, early withdrawal, tax and deposit-insurance terms in your own documents; this calculation does not establish them.