But the issue at present is that most of the tenants also signed leases at least five years ago, meaning the landlords are not able capture the underlying rental growth.

This is reflected in the average like-for-like income growth revealed in the latest reporting season, which ranged from negative to single digits.

This compares to the forecast rent rises, on average, but office leasing agents, of between 8 to 10 per cent in the coming two years, based on limited new supply entering the sector, across Sydney and Melbourne and the high absorption rates that have been forecast.

So to reap the high rental estimations, landlords need to be singing new leases now. But the problem for some is, in order to get developments off the ground, they need anchor tenants.

Most of the larger projects, such as Brookfield's $2 billion Wynyard site in Sydney's George Street, signed up tenants, in this case NAB, close to a year ago, quite possibly at the then market rents, which were lower than if they signed today.

Other landlords would be in the same position. IAG is moving to Darling Park later this year to replace PWC, but again that leasing deal was confirmed a year ago.

One way landlords are making inroads is offering more flexible and short term space to tenants that may have to move earlier and need temporary digs.

Luke Briscoe, managing director of office & industrial for AMP Capital, says offering flexibility to customers works for owners on a number of levels.

''Firstly, at its heart, it is delivering on the customer promise of providing a platform for their success. By providing flexibility, we are genuinely partnering with our customers to help their business thrive. A thriving business will continue to grow in our portfolio,'' Mr Briscoe said.

''Also, from an income perspective, right now in Sydney and Melbourne you’ll see great examples of where short-term leases can work for owners in a growing market.

''With the near record low vacancy, having a lease expire enables the owner to capture the strength of the market in any new leasing transaction. While a long term lease provides income security and remains preferred by investors, it can prevent owners from accessing the strong demand that exists at that time.”