Incentive levels are discounts landlords give to tenants in return for signing a lease.
Tenancy Matters director Chris Goodwin said landlords had been more generous with incentives than they were a year ago.
He said rental incentive levels for A-grade new office buildings were between 15% and 20% of the net face rent.
This compares with about 10% for existing A-grade buildings.
Last year, incentives for new office buildings were between 12% and 15% for buildings under construction, and between 8% and 10% for existing stock.
Mr Goodwin said he expected the market to tip firmly in favour of the tenant at the start of next year, when CBD office tenants started a game of musical chairs, leaving plenty of "backfill" space in their wake.