The Z-spread, ZSPRD, zero-volatility spread, or yield curve spread of a bond is the parallel shift or spread over the zero-coupon Treasury yield curve required for discounting a predetermined cash flow schedule to arrive at its present market price. The Z-spread is also widely used in the credit default swap (CDS) market as a measure of credit spread that is relatively insensitive to the particulars of specific corporate or government bonds.
Since the Z-spread uses the entire yield curve to value the individual cash flows of a bond, it provides a more realistic valuation than an interpolated yield spread based on a single point of the curve, such as the bond's final maturity date or weighted-average life. However, the Z-spread does not incorporate variability in cash flows, so a fuller valuation of an interest-rate-dependent security often requires the more realistic (and more complicated) option-adjusted spread (OAS).