Calculate the number of days from the start of the coupon period to the settlement date.

`COUPDAYBS(settlement, maturity, frequency, [basis])`

- Settlement - required, the date the security is transferred to the investor
- Maturity - required, the date when the investment ends and the principle plus accrued interest is returned to the investor
- Frequency - required, the number of interest payments per year
- Basis - [OPTIONAL] the day count basis

`=COUPDAYBS(DATE(2019,2,15),DATE(2024,1,1),2,0)`

This example uses the COUPDAYBS function to calculate the days from the coupon period to the settlement date using hardcoded arguments. The first argument is the start date of the coupon period (February 15, 2019), the second argument is the end date of the coupon period (January 1, 2024), the third argument is the frequency of coupon payments (2, meaning twice a year), and the fourth argument is the number of days from the settlement date to the next coupon payment (0, meaning the coupon payment is on the settlement date).

`=COUPDAYBS(C6,C7,C10,C11)`

This example uses the COUPDAYBS function to calculate the days from the coupon period to the settlement date for the values in C6, C7, C10, and C11. The first argument (C6) is the start date of the coupon period, the second argument (C7) is the end date of the coupon period, the third argument (C10) is the frequency of coupon payments, and the fourth argument (C11) is the number of days from the settlement date to the next coupon payment.

COUPDAYBS is a financial function which calculates the number of days from the start date of a coupon to its settlement date, using the US 30-day method and a 360-day year. It defaults to zero if omitted.

- The COUPDAYBS function takes four arguments: settlement, maturity, frequency, and basis. Basis is a number between 0 and 4 and determines how days are counted.
- The output of the COUPDAYBS function is an integer
- The output should use numeric formatting instead of date formatting to ensure it is displayed properly

The COUPDAYBS function is a financial function that calculates the number of days from the start of a coupon's period until the settlement date. This function uses the US 30-day method with a 360-day year, and defaults to 0 if not specified.

- Settlement Date (required)
- Maturity Date (required)
- Frequency (required)
- Basis (optional)

The default value of the COUPDAYBS function is 0 if not specified.