Members can make contributions into an SMSF.
You must meet the contribution rules for allowable member contributions in order to do so.
Like employer contributions, there are no limits on how much you can contribute. There are contribution cap limits that apply so tax excess contributions beyond the cap limits. Effectively, no SMSF member would probably want to exceed the limits because of the tax consequences.
Members may be able to claim a tax deduction for contributions made into the SMSF. This must be notified to the fund before the fund lodges it’s tax return and you must meet the requirements to be able to claim a deduction for these contributions – “concessional contributions”. And the contribution caps apply which will tax excess contributions above the cap.