The Reserve Bank of Australia’s cash rate, held at 4.35% since November 2023, has shifted the arithmetic of holding a home. Variable-rate repayments on a $750,000 loan now sit near $4,800 a month, a jump of roughly $1,400 since early 2022. The squeeze has turned thousands of owner-occupiers into landlords almost overnight: vacate the property, lease it at a market rent of $3,500 a month, and move into cheaper accommodation. When they do, they enter Division 118 of the Income Tax Assessment Act 1997 — and specifically the six‑year absence rule in s.118‑145, which can shelter an otherwise large capital gain. The Australian Taxation Office has sharpened its oversight at exactly the same moment. On 27 June 2023 it extended its Rental Property Income data‑matching program, now collecting transaction records on 1.6 million rental owners each year. Six weeks later, on 1 August 2023, it published Taxpayer Alert TA 2023/01, flagging it will audit taxpayers who claim the full main residence exemption on a rented‑out former home while simultaneously treating another dwelling as their main residence. With CoreLogic data showing Sydney dwelling values up 11.3% in the year to March 2024 and Melbourne up 4.2%, an incorrect application of the six‑year rule can produce a capital gains tax liability well past $150,000 on a median‑priced house. Lenders, too, watch the transaction carefully: Westpac caps assessable rental income at 80% of gross, APRA’s 3.0‑percentage‑point serviceability buffer pushes the assessment rate above 9.4% p.a., and non‑banks such as Pepper Money apply a 7.0% floor rate. The six‑year rule is now a live lending and tax‑planning event, not a footnote.
How the Six‑Year Absence Rule Actually Works
The law lets a homeowner continue treating a dwelling as their main residence for capital gains tax purposes for up to six years after they move out, provided they do not claim the exemption on another property during that absence. The rule is found in s.118‑145 of the ITAA 1997 and is administered by the ATO’s “Absence from your main residence” guidance, last updated 29 June 2023.
The central condition: no other main residence
A taxpayer can only apply the six‑year rule if, during the absence, no other dwelling is treated as their main residence. The exception is a six‑month overlap period allowed when buying a new home. After that overlap, the taxpayer must choose: keep the exemption on the former home or claim it on the new one. If they choose the new one, the old home immediately loses its main residence status and the absence rule ceases to apply from that date. Taxpayer Alert TA 2023/01, issued 1 August 2023, directly targets arrangements where a taxpayer attempts to retain the exemption on both the vacated property and a newly acquired residence by misapplying the six‑month overlap or by failing to elect which property is the main residence.
Counting the six years
The six‑year period is not a single continuous block by default; it is the total of all periods of absence during which the property is income‑producing and the no‑other‑main‑residence condition is met. If a taxpayer moves out, rents the home for four years, moves back and genuinely re‑occupies it as a main residence, then moves out again, a fresh six‑year clock starts from the date of the second departure. The ATO scrutinises “short” re‑occupations, examining the quality of the occupation. Moving back for a few months and then relisting the property for sale will often fail the test; the dwelling must actually be the taxpayer’s main residence. The “absence from your main residence” page on the ATO website warns that a mere intention to re‑establish main residence is insufficient without objective evidence — utilities, electoral roll registration, change of address on financial accounts.
The market value reset at the start of the rental period
A crucial, often overlooked, provision sits at s.118‑192. When a main residence first starts producing income, the property is treated for CGT purposes as having been acquired at its market value on the day it first earned rent. This means the cost base for calculating the capital gain is reset. The original purchase price is discarded. The effect is that the exempt portion of any future gain is limited to the increase in value after the property became a rental. Any latent gain built up during the genuine main residence period is quarantined and remains exempt, but all post‑rental growth is subject to the six‑year rule’s apportionment. Without a contemporaneous market valuation, the ATO will accept a valuation by a qualified valuer prepared later, but the taxpayer bears the risk of a dispute.
ATO Scrutiny and Taxpayer Alert TA 2023/01
The ATO’s compliance focus on rental property has intensified since 2023, driven by expanded data collection and a specific alert targeting the six‑year rule’s misuse.
Data‑matching that now captures every ‘accidental landlord’
The ATO’s Rental Property Income data‑matching protocol, extended on 27 June 2023, draws records from banks, property managers, state revenue offices and sharing platforms. It covers 1.6 million taxpayers, cross‑referencing rental income declared in tax returns with mortgage data, and flags discrepancies. A taxpayer who vacates a principal place of residence and begins renting it will appear in this dataset — the ATO knows the property has been vacated, the rent received, and whether a corresponding main residence exemption is claimed on another address. An unreported rental period combined with an exemption claim on a separate property is an automatic trigger for a compliance letter.
The double‑claim trap
Taxpayer Alert TA 2023/01 describes a scenario the ATO says is “prevalent”: an individual moves out of their main residence, rents it out, buys another home and moves in, then, when they later sell the original property, claims the full main residence exemption under the six‑year rule while also treating the newly acquired home as their main residence. The alert states the ATO will disallow the exemption on the rented property and may apply penalties of 25% to 75% of the tax shortfall. The only safe path is to elect one main residence at a time. Once a taxpayer starts treating the new home as their main residence for any purpose — such as using the main residence exemption to exempt its future sale — the six‑year rule on the old home terminates immediately.
What a short re‑occupation really achieves
A common defence is to move back into the rental property just before the six‑year mark and occupy it briefly before selling. The ATO’s TA 2023/01 and supporting rulings emphasise that the character of occupancy is tested by the taxpayer’s actual residential use. If the taxpayer continues to be registered on the electoral roll elsewhere, lets the utilities lapse, or moves minimal furniture in for a short period, the ATO will treat the re‑occupation as a “sham” and deny a fresh six‑year clock. To re‑establish main residence, the taxpayer must genuinely live in the dwelling as their home — typically evidenced by a period of at least six months of continuous occupation, relocation of personal effects, change of address for employment and financial records, and cessation of the rental stream.
Running the CGT Numbers
Calculating the CGT liability when the six‑year rule applies requires an understanding of the market‑value reset, the apportionment formula, and the interaction with the 50% CGT discount.
The apportionment formula
If the total period of absence covered by the rule is six years or less and no other main residence was claimed, the entire gain is exempt. If the absence exceeds six years, the exemption is apportioned. The exempt fraction is: [ \frac{\text{Days property was main residence (including absence days within the six‑year cap)}}{\text{Total ownership days}} ] Only the gain calculated from the market‑value cost base on the first day of income production is subject to this fraction. Any gain attributable to the period before the first rental is fully exempt regardless. The ATO expects the calculation to be done in days.
A worked example
Suppose a Sydney apartment was bought in July 2015 for $850,000. The owner lived there as their principal residence until July 2020, when they moved out and rented it. A qualified valuer determined the market value at July 2020 to be $1,100,000. The apartment was rented continuously and sold in September 2027 — absence of 7 years and 2 months, exceeding the six‑year cap by 14 months. Total ownership 12 years and 2 months (4,450 days). Days of main residence plus capped absence: 5 years owner‑occupied (1,825 days) + 6 years of absence (2,190 days) = 4,015 days. Exempt portion = 4,015/4,450 = 90.2%. The capital gain for CGT is sale price $1,650,000 less cost