ABN Work / withholding payment of invoice

Hello,

I was until recently working as a sub contractor through my ABN number. I decided to quit my job last week thursday.

I have since been waiting for the payment of my last invoice, which was sent Monday and promised to be paid on Tuesday this week.

Now my "boss", is telling me that he will be holding payment until progress on the job is done, because he can't pay for now.

Is this legal? How long can he withhold from paying this invoice?

Thanks in advance for your advice!