The sentence cannot be parsed in my opinion and is thus nonsense.
Maybe the sentences around it shed some light?
The center part can be removed, as it adds info to the remaining parts.. so it can be removed for the moment.
this part can be removed
'from the date on which the hiring is determined or comes to an end, less a rebate of interest on all rentals falling due after the date of termination'
leaving
"The balance of the rentals payable on foot of this Agreement, at the discount rate of 5%."
which makes no sense... although it would if the words 'are payable' are inserted before 'at the discount rate'.
This would give
"The balance of the rentals payable on foot of this Agreement, are payable at the discount rate of 5%."
It appears as if you end your agreement early, then you must pay 5% of the contracted charges you would otherwise have paid.
But the center part I removed earlier also makes no sense...
'from the date on which the hiring is determined or comes to an end, less a rebate of interest on all rentals falling due after the date of termination'
The words 'is determined' make no sense... and the whole phrase
'from the date on which the hiring is determined or comes to an end'
doesn't really make sense...
it would if
'is determined or'
was removed leaving
'from the date on which the hiring comes to an end'
So with my changes..
"The balance of the rentals payable on foot of this Agreement, from the date on which the hiring comes to an end, less a rebate of interest on all rentals falling due after the date of termination, is payable at the discount rate of 5%."
Actually, it still makes no sense... as this seems like nonsense
'less a rebate of interest on all rentals falling due after the date of termination'
Edited to add. Perhaps it makes sense if you pay both rental and interest now... and if you end your contract early you may have to pay 5% of the rental only, and no interest.