Under the Foreign Acquisitions and Takeovers Act 1975, foreign persons may be required to submit a notification before acquiring an interest in commercial land in Australia. Agricultural land is covered by separate rules.
In the case of vacant commercial land, a notification is generally needed regardless of the value of the proposed acquisition. As for developed commercial land, private foreign investors need to notify the planned acquisition only if it exceeds a specific monetary threshold. A higher threshold applies for investors from certain countries with which Australia has free trade agreements. 
A land acquisition which meets the threshold test can be prohibited by the Treasury if considered to be contrary to the 'national interest'. The national interest, and what would be contrary to it, is not defined in the Act or the Foreign Acquisitions and Takeovers Regulation 2015. Assessments are made on a case-by-case basis. However, a Foreign Investment Policy document states that the Government typically considers the following factors when assessing foreign investment proposals: national security; competition; other Australian government policies, including tax; impact on the economy and the community and the character of the investor. 
Certain acquisitions are exempted from reviews by virtue of the 2015 Regulation. Generally, acquisitions by foreign non-government acquirers of an interest in Australian land from the Commonwealth, a State, a Territory or a local governing body of Australia or an entity wholly owned by the Commonwealth, a State, a Territory or a local governing body, are exempted from reviews. However, acquisitions of an interest in Australian land if the interest is, or includes, certain infrastructure assets, are excluded from the exemption. These infrastructure assets include 'public infrastructure', which is defined in the Regulation as including also electricity generation, transmission, distribution and supply systems and facilities.
"4  Dictionary of definitions
In this Act: […]
Australian land means agricultural land, commercial land, residential land or a mining or production tenement. […]
commercial land means land in Australia or the seabed of the offshore area, other than land:
(a) used wholly and exclusively for a primary production business; or
(b) on which there is at least one dwelling (except commercial residential premises); or
(c) on which the number of dwellings (except commercial residential premises) that could reasonably be built is less than the number prescribed by the regulations for the purposes of subparagraph (a)(ii) of the definition of residential land in this section. [...]
foreign person means:
(a) an individual not ordinarily resident in Australia; or
(b) a corporation in which an individual not ordinarily resident in Australia, a foreign corporation or a foreign government holds a substantial interest; or
(c) a corporation in which 2 or more persons, each of whom is an individual not ordinarily resident in Australia, a foreign corporation or a foreign government, hold an aggregate substantial interest; or
(d) the trustee of a trust in which an individual not ordinarily resident in Australia, a foreign corporation or a foreign government holds a substantial interest; or
(e) the trustee of a trust in which 2 or more persons, each of whom is an individual not ordinarily resident in Australia, a foreign corporation or a foreign government, hold an aggregate substantial interest; or
(f) a foreign government; or 
(g) any other person, or any other person that meets the conditions, prescribed by the regulations. [...]
land includes:
(a) a building (including a new dwelling or an established dwelling) or a part of a building; and
(b) subsoil of land.
[...]
12  Meaning of interest in Australian land
(1) An interest in Australian land (however described) is:
(a) a legal or equitable interest in Australian land, other than:
(i) an interest under a lease or licence or in a unit in a unit trust; or
(ii) an interest in an agreement giving a right (known as a profit à prendre) to take something off another person’s land, or to take something out of the soil of that land; or
(iii) an interest in an agreement involving the sharing of profits or income from the use of, or dealings in, Australian land; or
(b) an interest in a security in an entity that owns Australian land, being a security that entitles the holder to a right to occupy a dwelling of a kind known as a flat or home unit situated on the land; or
(c) an interest as lessee or licensee in a lease or licence giving rights to occupy Australian land if the term of the lease or licence (including any extension or renewal) is reasonably likely, at the time the interest is acquired, to exceed 5 years; or
(d) an interest in an agreement giving a right of a kind mentioned in subparagraph (a)(ii) if the term of the agreement (including any extension or renewal) is reasonably likely, at the time the interest in the agreement is acquired, to exceed 5 years; or
(e) an interest in an agreement involving the sharing of profits or income from the use of, or dealings in, Australian land if the term of the agreement (including any extension or renewal) is reasonably likely, at the time the interest in the agreement is acquired, to exceed 5 years; or
(f) an interest in a share in an Australian land corporation or agricultural land corporation; or
(g) an interest in a unit in an Australian land trust or agricultural land trust; or
(h) if the trustee of an Australian land trust or agricultural land trust is a corporation—an interest in a share in that corporation.
(2) An interest is an interest in Australian land even if it is the only interest that exists in the land or other thing concerned.
(3) A person acquires an interest in Australian land even if:
(a) the person has previously acquired an interest in Australian land; or
(b) the interest is an increase in the amount of an existing interest of the person in Australian land.
[...]
43  Meaning of significant action—land
An action is a significant action if:
(a) the action is for a foreign person to acquire an interest in Australian land; and
(b) the threshold test is met in relation to the land (see Subdivision B of Division 4).
[...]
47  Meaning of notifiable action—general
(1) An action is a notifiable action if the conditions in this section are met.
First condition—kinds of action
(2) The first condition is that the action is any of the following: [...]
(c) to acquire an interest in Australian land.
Second condition—threshold
(3) The second condition is that the threshold test is met in relation to the entity, business or land (see Subdivision B of Division 4). [...]
(5) The last condition (whether paragraph (2)(a), (b) or (c) applies) is that the action is or is to be taken by a foreign person.
[...]
52  The threshold test for land
Land without threshold value
(1) The threshold test is met in relation to land if the land is of a kind that is prescribed by the regulations for the purposes of this subsection.
Agricultural land where total value of interests is above threshold value
(2) The threshold test is met in relation to land if both of the following apply:
(a) the land is agricultural land;
(b) the total value of the following is more than the value prescribed for the purposes of this paragraph:
(i) all interests in agricultural land held by the foreign person, alone or together with one or more associates;
(ii) the consideration for the acquisition of the interest in the land.
Other land where value of interest is above threshold value
(3) The threshold test is met in relation to land if both of the following apply:
(a) the land is not land prescribed for the purposes of subsection (1) or agricultural land;
(b) the value of the interest in the land is more than the value prescribed for the purposes of this paragraph.
[...]
67  Order prohibiting proposed significant actions
(1) The Treasurer may, by notifiable instrument, make an order under subsection (2) if the Treasurer is satisfied that:
(a) a significant action is proposed to be taken; and
(b) taking the significant action would be contrary to the national interest.
(2) The Treasurer may make an order in accordance with the following table.
[see legal source for table]
[...]
81  Compulsory notice of notifiable actions
(1) A foreign person who proposes to take a notifiable action must give a notice to the Treasurer before taking the action.
(2) If a person takes an action by entering an agreement, the notice must deal with each notifiable action covered by the agreement." (Foreign Acquisitions and Takeovers Act 1975 (Act No. 92 of 1975), last amended 18 September 2018, Sections 4, 12, 43, 47, 52, 67 and 81)
----------------------
"5  Definitions
Note: A number of expressions used in this instrument are defined in the Act, including the following: [...]
(c) Australian land; [...]
(e) foreign person; [...]
vacant:
(a) land is vacant if there is no substantive permanent building on the land that can be lawfully occupied by persons, goods or livestock; but
(b) despite paragraph (a), land is not vacant if a wind or solar power station is located on the surface of the land.
[...]
28  Application of this Division
This Division applies to the provisions of the Act, other than:
(a) the definition of foreign person in section 4 of the Act; and
(b) any other provision of the Act to the extent that it relates to that definition.
The provisions of the Act that this Division applies to are the excluded provisions.
[...]
31  Australian businesses carried on by or land acquired from government
(1) The excluded provisions do not (subject to subsection (2)) apply in relation to an Australian business that is carried on (whether alone or together with one or more other persons) by, or an acquisition of an interest in Australian land from, any of the following persons:
(a) the Commonwealth, a State, a Territory or a local governing body;
(b) an entity wholly owned by the Commonwealth, a State, a Territory or a local governing body.
(2) However, subsection (1) does not apply in relation to:
(a) an acquisition of an interest by a foreign government investor; or
(b) an acquisition of an interest in Australian land if the interest is, or includes, an interest in any of the following infrastructure:
(i) public infrastructure, except in relation to public roads;
(ii) infrastructure for existing or proposed roads, existing or proposed railways, or existing or proposed inter‑modal transfer facilities, within the National Land Transport Network (within the meaning of the National Land Transport Act 2014);
(iii) infrastructure for existing or proposed roads, existing or proposed railways, or existing or proposed inter‑modal transfer facilities, that are designated under a law of a State or Territory as either significant or controlled by the State or Territory;
(iv) the infrastructure (or part of the infrastructure) of a telecommunications network;
(v) a nuclear facility; or
(c) an Australian business that holds an interest in Australian land to which paragraph (b) applies.
[...]
52  Land
Land without threshold value
(1) For subsection 52(1) of the Act, the following land is prescribed:
(a) residential land, except residential land covered by subsection (2);
(b) commercial land that is vacant;
(c) a mining or production tenement, except a tenement being acquired by a relevant agreement country investor;
(d) land (including land otherwise covered by subsection (4) or (5)) acquired by a foreign government investor;
(e) land held by an Australian land corporation or the trustee of an Australian land trust (except an agricultural land corporation or an agricultural land trust) if:
(i) the interest in Australian land that is acquired by a foreign person is an interest in a share in the corporation or a unit in the trust; and
(ii) the land is not covered by subsection (3).
(2) Residential land is covered by this subsection if:
(a) the land is also commercial land that is not vacant; and
(b) the area of land that is residential land (excluding any commercial residential premises) is less than 10% of the total area of the land; and
(c) the value of the land that is residential land (excluding any commercial residential premises) is less than 10% of the total value of the land; and
(d) a reasonable assessment of the area and value of the land was made in determining that the land is covered by paragraphs (b) and (c).
Land held by Australian land corporation or trustee not covered by subsection (1)
(3) Land held by an Australian land corporation or the trustee of an Australian land trust is covered by this subsection if:
(a) the total value of interests in residential land, and commercial land that is vacant, (except interests in land covered by subsection (3A)), that are held by the corporation or trustee is less than 10% of the value of the total assets of the corporation or trustee; and
(b) a reasonable assessment of the value of the interests was made in determining that the land is covered by paragraph (a).
(3A) The following land is covered by this subsection:
(a) residential land covered by paragraph 38(5)(a);
(b) residential land covered by subsection (2) of this section.
Threshold value for agricultural land
(4) The following table prescribes a value for paragraph 52(2)(b) of the Act (agricultural land). [...]
Threshold value for any other land
 (5) The following table prescribes values for paragraph 52(3)(b) of the Act (any other land). [see legal source for table][...]" (Foreign Acquisitions and Takeovers Regulation 2015 (SLI 2015 No. 217), last amended 30 December 2018, Sections 5, 28, 31, and 52)
Foreign Acquisitions and Takeovers Act 1975 (Act No. 92 of 1975), last amended 18 September 2018, Sections 4, 12, 43, 47, 52, 67 and 81
Foreign Acquisitions and Takeovers Regulation 2015 (SLI 2015 No. 217), last amended 30 December 2018, Sections 5, 28, 31, and 52
[<a href="https://www.legislation.gov.au/C2004A01402/2018-09-18/text">Act</a>],[<a href="https://www.legislation.gov.au/F2015L01854/2018-12-30/text">Reg</a>]