To claim a tax deduction for super contributions (as an employer or as an individual), the payment needs to be received by the fund no later than 30 June. Merely incurring a liability is not enough.
If you are making a personal superannuation contribution that you want to claim as a tax deduction, you need to write to your fund in their approved form and advise them of the amount you intend to claim as a deduction. The superannuation fund then needs to acknowledge your notice of intent and agree to the amount you intend to claim as a deduction. This will normally be in the form of a notice or certificate from the fund to confirm the tax deductibility of the contribution.