How can you pay for Sydney harbor tunnel?

If you have already gone through the tunnel or one of Sydney's other cashless toll roads, you must buy an E-pass within 48 hours of your trip. This is done by going to http://www.rta.nsw.gov.au/usingroads/etoll/pass/index.html and filling out the form for the E-toll pass. Please be informed, you are not to buy an e-toll TAG, but an E-toll PASS. You must purchase an E-pass unless you already have an e-tag, which you would know if you did.