The Limit Yield is the minimum yield (return before fees) that you are willing to accept for the bond.
During the Bond IPO, the issuer will determine the Final Yield. If the Final Yield is lower than the Limit Yield you specified, your application will not be eligible for allotment.
Example:
You submit a Bond IPO application with a Limit Yield of 4.20%.
After the subscription period, the issuer announces a Final Yield of 4.00%.
Since 4.00% is lower than your minimum acceptable yield of 4.20%, your application will not be allotted.
On the other hand:
You submit a Limit Yield of 4.00%.
The issuer announces a Final Yield of 4.20%.
Since the Final Yield meets or exceeds your Limit Yield, your application remains eligible for allotment (subject to the issuer's allotment process).
Note : A lower limit yield makes your bid more competitive, but does not guarantee allotment and remains subject to overall demand and the timing of your submissions.