ATO have recently provided the following information on their website
Income tax deduction
We understand this system maintenance may impact on the timing of your payment to the SBSCH. So that you are not disadvantaged, the Commissioner won't apply compliance resources to consider whether the contribution you made was received by the super fund in the same financial year you made the payment to the SBSCH, if the following applies:
- your payment was accepted by the SBSCH by 30 June 2019
- the amount has not been dishonoured or returned to you
- you would otherwise be entitled to the deduction.
Note that for the purpose of the Individuals Contribution Cap the date the money is received into the Super fund will determine the financial year in which it is received.
Noting that clearly if the payment is paid into the SBSCH by 30 june then it meets the requirements for SG purposes as it will ahve been paid before 28 July.