It is the first of the reductions in the suite of support measures put in place by the Morrison government in April as it sought to protect the incomes of people facing unemployment.
Analysis by Deloitte Economics shows there are about 2.3 million receiving the supplement,with the cut in the payment reducing their collective monthly incomes by $1.5 billion.
It estimates about 85 per cent of the supplement is being spent,cutting possible expenditure by $1.3 billion a month.
Total fiscal support peaked at $16.6 billion a month in June,with that forecast to fall to just $600 million by June next year.
"The emergency Band-Aids are starting to come off,"Deloitte Access director Chris Richardson said.
Social Services Minister Anne Ruston said the supplement was always a temporary measure but the government had extended it,albeit at a lower rate,until the end of the year.
"As the economy starts to reopen,we believe it is important to balance that enhanced support with incentives to reconnect with the workforce,which is why we are increasing the amount JobSeeker recipients can earn before it affects their payment to $300 per fortnight,"she said.