INVESTMENTS
Investment calculations: eurobonds, Treasury bills and funds
The Investment screen covers three instruments: eurobonds, Treasury bills and government bonds, and investment funds. You enter the price and the exchange rate from your bank, your broker or the contract note. Bankacı works out the return and the withholding and, for a eurobond, whether the year needs a return and the estimated extra tax. The calculation is in the app and the member portal; this page explains how it is worked out.
Updated: 12 October 2026
Eurobonds
Pick one of the Treasury's dollar and euro eurobonds from the list; the coupon, maturity, currency and day count fill in on their own. For a Turkish bank's or company's bond, or a foreign issuer's, these come from the prospectus. It asks for the nominal, the trade date, the settlement date, the price and the exchange rate, and for a sale the same again. The result shows the purchase and sale amounts, the yield to maturity and current yield, the return in the bond's currency and in lira, the year's coupons, the gain on the sale, whether a return is needed and the estimated extra tax. The yield to maturity follows the bond's own rules: 30/360 and two coupons a year on a dollar bond, actual days and one coupon a year on a euro bond. In the last coupon period, on a euro bond too, what is left is discounted at simple interest.
Treasury bills and government bonds
Choose a discount bill or a fixed-coupon bond. Enter a price or a yield; from a yield the price is found. Choose the day basis, 364 (auction) or 365 (secondary market). On a coupon bond the coupon days are found by counting back from maturity in steps of 182 days, and accrued interest is the coupon × days run / 182. The result shows what is paid and what is received, the withholding, the period yield, the simple and compound annual yields and the matching term deposit rate. CPI-linked and TLREF-linked bonds are not calculated.
Investment funds
Choose the fund type and enter each purchase by date, price and number of shares or amount; several purchases can be added. Enter the sale's date, price and shares. The sale is split across the purchases first in, first out, and each slice pays its own purchase day's rate; a slice's loss comes off the same sale's slices at a gain (GVGT 258). The result shows the cost, the proceeds, the gross gain, the withholding, the net gain, the period return and the annual return as an internal rate.
How the tax is worked out
For a eurobond the order follows GİB's guides: residence first, then the withholding on the coupons, the indexing of the gain on a sale by the producer price index, the 86/1-d test for a foreign issuer's coupon and finally the 86/1-c test. The estimated extra tax is the difference between two returns, one with the bond and one without; the year's other income goes under details. On Treasury bills and funds the withholding is final and the rate follows the purchase day. The rates, limits and dates are kept in the app with their sources.
Assumptions
Bankacı makes no offer; you enter the price and the rate. The producer price index comes from the app's own table; a month the table lacks is typed in. A coupon is converted at the TCMB buying rate in force on the day it is paid. Accrued interest received on a sale goes into the sale proceeds by default; it can be counted as interest income instead. One bond and one tax year are calculated. No tax is worked out for someone whose wage is declared too, or for a bond received by transfer or inheritance. The result is general information, not tax advice; speak to a certified accountant before you file a return.
Frequently asked
Does the Investment calculator replace tax advice?
No. The result is general information based on what you enter and the rules in force on the day. Where the administration's view is not settled, the screen says which assumption it used. Speak to a certified accountant before you file a return.
Does Bankacı fetch the prices and exchange rates?
No. You enter the price from your bank, your broker or TEFAS, and the rate from TCMB or the contract note. A Treasury eurobond's coupon and maturity, and the producer price index, come from the app's own tables.
Which eurobonds are on the list?
The Treasury's dollar and euro eurobonds not yet matured: HMB's list of 31 August 2026, brought up to 10 October 2026 with later issues and redemptions. The dollar sukuk and the yen bond are not on it; company and foreign issuers' bonds are entered by hand.
Is the Investment calculator free?
Yes. It is free in the app, with no Premium.
See also: Term deposit calculation · Daily-earning account calculation · Eurobond tax 2026 · Investment fund withholding tax · Treasury bill yield and withholding
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