How Bond Day Count Affects Coupons and Accrued Interest

Summary

The document clarifies why a semiannual bond schedule can place payments on recurring calendar dates even when adjacent periods do not contain exactly 180 actual days. In many markets, the coupon amount is set as the annual coupon rate divided by the stated payment frequency. The day-count convention does not determine the coupon schedule or scale that regular coupon payment in those cases.

Instead, day count is commonly used to calculate accrued interest between coupon dates when a bond trades, allowing the clean price to be converted to a full price. The answer also notes that practice varies: some markets and instruments, including certain loans, swap legs, and bonds, calculate fixed payments using day-count fractions. The explanation is a general convention, not a universal rule, so market and instrument terms must be checked when modeling a specific bond.

Key ideas

• Semiannual coupon dates can follow calendar intervals that differ in actual day length.
• In many bond markets, coupon payments are based on the stated annual rate and payment frequency.
• Day count commonly determines accrued interest between coupon dates and the full price.
• Conventions vary across markets and instruments, so the applicable terms must be verified.

Tags

# 30E/360 bond payment schedule


# 30E/360 bond payment schedule












I have a bond that was issued on the 30th of April with 30/360 European day convention basis and semiannual compounding. As far as I understand payments should be every 180 days according to the day convention, but with quantlib schedule, I got payments on every 30th of October and April, which are not 180 days from each other. Is there something wrong with quantlib or doesn't day conventions just affect the payment schedule?

## Answer by Dimitri Vulis (score 1, accepted)

https://quant.stackexchange.com/a/68188

In the U.S., the U.K., and most (but not all!) other markets, the convention is: the daycount isn't used to calculate how much bond coupon is paid. Rather, it is exactly 1/frequency of the indicated coupon rate per annum, even though the coupon period might be 181 or 182 actual days. (In contrast, fixed coupons are daycounted for loans (and loan participation notes), and for swap legs in the U.S., and also for bonds in some other markets.)

The daycount is used, however, to calculate the accrued until the settlement date, if you trade the bond in the middle of a coupon period, and hence to calculate the full price from a clean price.

Shown in full with attribution under the source's licence. Licence: CC BY-SA 4.0 (Stack Exchange)

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.