Aug 24 (Reuters) - Investa Office Fund IOF.AX
* announces an on-market buy-back of up to 5% of iof stapled securities
* the distribution is anticipated to increase by 0.5%, with distribution guidance for financial year 2018 of 20.3 cents per unit
* Funds from operations guidance for financial year 2018 is 30.0 cpu, up 1.0 percent
* for fy the fund generated an 18.0% return on equity