yield to call is an investor’s overall return for owning a bond should it be called in prior to maturity by the issuer.
Applying "Yield to Call" to Securities Exams:
When an investor purchases a bond that can be called in for redemption by the issuer the investor needs to be aware of how their return can be impacted by the bond being called. If a bond is called in it will reduce the holding period of the bond. If the bond was purchased at a discount the appreciation to par will happen more quickly. As a result the yield to call will be the highest yield for an investor who purchases a callable bond at a discount. Alternatively, if an investor purchased the bond at a premium and the bond is called the investor will have less time to amortize the premium and the yield to call will be the lowest yield.