Commuters who use the Opal card readers on Illawarra stations before they are officially launched risk being fined for fare evasion.
The issue came to light after an Illawarra commuter managed to successfully tap on with his Opal card at a reader on North Wollongong Railway Station on Saturday.
Asanga Jayawardana said he was "really, really interested" in the new technology and once he saw the card readers at North Wollongong he ordered an Opal card and downloaded the My Opal app for his phone.
Catching the train at North Wollongong to Petersham on Saturday, he decided to try the card.
"Before I tapped on the card, I had a look on all poles which were installed," Mr Jayawardana said.
"There were some poles being tested and stickers were pasted on some poles, but one was working. I tapped on and it displayed the current balance on a green display, which was correct."
On his return journey, several ticket inspectors boarded the train at Waterfall station.
They asked Mr Jayawardana for his ticket and he showed his Opal card, only to be told the card did not work that far south.
He then showed his My Opal app and its record of his fare payment as proof that he had paid and the inspector accepted this.
However, Transport for NSW said commuters who used the Opal equipment before the go-live date would not be travelling with a valid ticket and risked being fined.
Travelling without a valid ticket can attract an on-the-spot fine of $200 or a maximum fine of $550.
Transport for NSW also stated it did not offer or endorse any Opal card mobile applications. Apps such as Mr Jayawardana's My Opal app have been developed by third parties and do not have any official relationship to the Opal card.
"Opal is currently available at 120 train stations," a Transport for NSW spokesman said.
"At other stations where equipment has already been installed, signs are in place and staff are asked to remind customers not to use Opal while it's still in test mode."