Yes. A business needs to satisfy the decline in turnover test only once in order to become eligible for the JobKeeper payment. Once the test has been passed once, there is no requirement to retest in later months.
One of the main design features of the Coronavirus JobKeeper payment is that it is available only to businesses that have experienced a sufficient reduction in turnover post-Coronavirus as compared with their turnover prior to the crisis. As you would expect, businesses that have not suffered as a result of the crisis – think supermarkets, courier companies, and cloud based software for example – should not, and cannot, get the payment.
But interestingly, a business that qualifies for the JobKeeper payment because it experiences an immediate reduction in turnover, will not lose its entitlement to the payment if and when its turnover rebounds. This is obviously good news for businesses that have been clever enough to reinvent themselves to meet the demands of a ‘socially distanced’ market.