Keep Back is used to withhold a certain amount of money in a property when generating payments. You may choose to only withhold a portion (or the entire amount) of what is available to pay.
You can enter the amount to Keep Back by editing the Property. It is also good practice to enter a reason for the Keep Back. Both the amount and reason will show on the Owner Statement.
It is different to putting an Owner on Hold which withholds all the money in the Owner account. You can put an Owner on Hold by selecting Hold from the Payment Type drop-down when editing an Owner.