This article describes the formula syntax and usage of the COUPDAYBS function in Microsoft Excel.

Description

The COUPDAYBS function returns the number of days from the beginning of a coupon period until its settlement date.

Syntax

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

Important: Dates should be entered by using the DATE function, or as results of other formulas or functions. For example, use DATE(2008,5,23) for the 23rd day of May, 2008. Problems can occur if dates are entered as text.

The COUPDAYBS function syntax has the following arguments:

• Settlement    Required. The security’s settlement date. The security settlement date is the date after the issue date when the security is traded to the buyer.
• Maturity    Required. The security’s maturity date. The maturity date is the date when the security expires.
• Frequency    Required. The number of coupon payments per year. For annual payments, frequency = 1; for semiannual, frequency = 2; for quarterly, frequency = 4.
• Basis    Optional. The type of day count basis to use.

Basis	Day count basis
0 or omitted	US (NASD) 30/360
1	Actual/actual
2	Actual/360
3	Actual/365
4	European 30/360

Remarks

• Microsoft Excel stores dates as sequential serial numbers so they can be used in calculations. By default, January 1, 1900 is serial number 1, and January 1, 2008 is serial number 39448 because it is 39,448 days after January 1, 1900.
• The settlement date is the date a buyer purchases a coupon, such as a bond. The maturity date is the date when a coupon expires. For example, suppose a 30-year bond is issued on January 1, 2008, and is purchased by a buyer six months later. The issue date would be January 1, 2008, the settlement date would be July 1, 2008, and the maturity date would be January 1, 2038, 30 years after the January 1, 2008, issue date.
• All arguments are truncated to integers.
• If settlement or maturity is not a valid date, COUPDAYBS returns the #VALUE! error value.
• If frequency is any number other than 1, 2, or 4, COUPDAYBS returns the #NUM! error value.
• If basis < 0 or if basis > 4, COUPDAYBS returns the #NUM! error value.
• If settlement ≥ maturity, COUPDAYBS returns the #NUM! error value.

Example

Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.

Data	Description
25-Jan-11	Settlement date
15-Nov-11	Maturity date
2	Semiannual coupon (see above)
1	Actual/actual basis (see above)
Formula	Description	Result
=COUPDAYBS(A2,A3,A4,A5)	The number of days from the beginning of the coupon period to the settlement date, for a bond with the above terms	71