This thread is a reference to Chapter 7 of the ASX Listing Rules -

As the title suggests the Chapter deals with changes in a company's capital and new issues.

In particular rules 7.29 to 7.35 deal with on market buy-backs.

Rule 7.33 states-

"A company may only buy back shares under an on-market buy-back at a price which is not more than 5% above the average market price for securities in that class. The average is calculated over the last 5 days on which sales in the shares were recorded before the day on which the purchase under the buy-back was made."

This rule is quoted as defining the highest price a company can pay for buy-back shares on a particular day.
This is pertinent to the LNC buy-back which is currently in progress.