Rates

[fransuaJoubert]

Currently one of our customers uses a rate structure for a minimum tariff, combined with a block tariff for water consumption . This is working fine but they now request the following:
If the customer uses less than 5 kl of water he will be invoiced a tariff excluding the VAT.
If he consumes more than 5 kl of water, he will pay for all consumption and VAT should be applied to the total consumption .
If ZERO consumption was recorded the minimum tariff should apply which is VATABLE.
Is this possible without any customization?
Please advise