99年合約的意思就是政府如果需要，99年合約期滿後可以無條件收回土地

感覺和中國的70年土地使用權沒有區別.但法律明確說明如果到時政府對土地沒有需要，土地所有人可以再使用99年.

http://www.actpla.act.gov.au/topics/property_purchases/leases_licenses/leasehold

Leasehold

Leasehold is a system of land tenure. You buy the right to use land under a lease for a term of 99 years. In every practical way, though, you build your house and own it just as you would anywhere else in Australia.

Lease and development conditions

When undeveloped blocks of land in the ACT are to be released for building, lease and development conditions are usually prepared for the blocks. The ACT Planning and Land Authority must approve these conditions. If you are considering buying a lease from the Territory or a land developer, you are entitled to and should seek a copy of the lease and development conditions from them. You can also check the Lease and Development Conditions Register.

Lease availability

Leases over individual blocks of land are not issued until all the necessary roads and services around them are completed, however they are often advertised for sale or ballot earlier. You will therefore usually have to rely on the lease and development conditions for information about what you are buying.

You will not be registered as the registered proprietor of the lease until it is legally granted or transferred to you. You may not be able to borrow money from a bank or other financial institution until the lease is available. You will not be able to start building until you are granted the lease or the lease is transferred to you and until you have an approved development application for the building.

Length of leases

Most residential leases in the ACT are granted for a term of 99 years. With such grants, the registered proprietor (or Crown lessee) is granted certain rights in relation to that leased land. One of those rights is the exclusive use and enjoyment of the leased land for the duration of the lease. However, the Territory may acquire the whole or part of the leased land for public purposes. In addition, if the lease has a withdrawal clause, the Territory may withdraw the whole or part of the leased land, where such withdrawal does not have to be for a public purpose. Provided that the land is not required by either the Territory or Commonwealth, the Territory will grant a new residential lease towards the end of the 99 years, to the person holding the old residential lease, without payment (other than an administrative fee). This gives the lessee continuing security of tenure.

Selling land in the ACT

As a Crown lessee, you can sell your Crown lease provided you have completed the building required by the building and development covenant contained in the lease or obtained consent.