Please could someone who has claimed a s10(1)(o)(ii) deduction on a tax return provide me with some clarity?

I have a client who was sent overseas for work (by his local employer) for more than 183 days in a 12 month cycle (including a period of more than 60 consecutive days) and I'm trying to find out if he can claim a deduction for the income he earned (locally in ZAR) during the period while he was out of the country. If so, how does this work practically? What does one have to provide to SARS in order to prove this deduction?

Any help with this query would be greatly appreciated.