What Duolingo score do you need for the University of Waikato?

The undergraduate document says all test results are valid for two years from the test date to the proposed start date. The postgraduate document says requirements must be met within one sitting, or on one certificate, unless stated otherwise.

For comparison, the entry requirements page asks for IELTS Academic 6.0 with no band below 5.5 for undergraduate study and 6.5 with no band below 6.0 for postgraduate.

Both documents list English language programmes and prior study in English as other ways to meet the requirement. Prior study in English is valid for two years from completion, or five years in some cases with further English-medium study or work.

Requirements vary by programme and change between admissions cycles. The score that binds you is the one on your Waikato programme page and in your offer letter, so check it there before you book a test.