Step 1: Meaning of discount on shares.
When a company issues its shares at a price below face value, the difference is called “discount on issue of shares”.
Step 2: Nature of loss.
This is not a trading (revenue) loss, because it is not related to day-to-day operations. It is connected with capital raising. Hence, it is a capital loss.
Step 3: Conclude.
Thus, discount on issue of shares is treated as a capital loss.
Final Answer:
\[
\boxed{\text{Capital loss}}
\]