Looking at the NSW legislation for these agency trust accounts, s 86 PROPERTY, STOCK AND BUSINESS AGENTS ACT 2002
http://www.austlii.edu.au/au/legis/nsw/consol_act/psabaa2002385/s86.html
86 Trust money to be paid into trust account
(1) Money received for or on behalf of any person by a licensee in connection with the licensee?s business as a licensee:
(a) is to be held by the licensee or (if the licensee is employed by a corporation) by the corporation, exclusively for that person, and
(b) is to be paid to the person or disbursed as the person directs, and ....
If the tenant pays money into the trust account for the landlord to hold for the landlord then there are 2 possibilities.
1. It is the tenant's money until that week/months rental income becomes payable. Therefore it is not derived as income by the landlord until the week or month it falls due.
or
2.. It is the landlord's money at the point of receipt. Therefore all accrued when paid.
Which one applies will depend on the instructions of the tenant - which would most likely be 'here is the rent' sort of thing which wouldn't help.
I guess the question to ask is if the tenant paid 6 months in advance but moved out after 1 month who would be entitlted to the other 5 months rent?
Arther Murray was a case that involved a dance instructor recieving payments for multiple dance classes up front. But it was determined the income was only derived once the lessons were given as there was a chance that the payments in advance could be refunded - ie they were contingent on the dance class actually happening.
The case with the rent is similar, but it involves a trust account, so I am inclined to say the tenant could argue that the money is still their's until it falls due and payable.
s 33 of the RTA (NSW) also prohibits a landlord requiring a tenant from paying more than 2 weeks in advance.
I am away from my books, but there may be caselaw which says otherwise.