Looking at a post about the possible difference between strip and principal T-bond interest rates should be equal. This question also relates duration, ie answer can be done using duration notion. In theory when we use formulas to calculate coupon bond value or correspondent duration the calculate formulas use the same interest rates for future maturities. On the other hand all "risk free' interest rates [$]r = r ( t , t_i ) = r ( t , t_i - t )[$] where [$]t_i[$] are coupon payment dates. Also if we wish to take into account liquidity aspect for coupon bond valuation we should use ask prices as far as to get payment c at [$]t_i[$] we should buy zero coupon bond at t for ask price. These facts can effect on the difference between strip and principal rates.