Good Day

We have 4 employees travelling overseas in the next few months. We will be providing them with a daily allowance while out of South Africa

1. Must this be put through the payroll as an allowance, and taxes deducted?
2. What will be the best way to manage this?
3. Or will it be best to pay them the allowance, upon return balance the expenses with proof of purchases provided, and then amount left over will then be processed as an extra income on their side through payroll?