Applicants previously had to submit forms through the post or via an antiquated online application process with low take-up, according to the Cabinet Office.
The service was tested on users for over a year before launch, with 125,000 digital claims submitted since it started being trialled in October 2013.
The government claimed a user satisfaction rate of 90 percent during beta testing and said 54 percent of claimants are now using the new online system, a third of them using their phone or tablet.
The launch means eight of the government's 25 'digital exemplars' are now live.
It joins new online services for student finance, online voter registration, patent renewal, viewing your driving licence, filing civil claims, lasting power of attorney applications and prison visit booking.
The new digital services are being redesigned by departments, led by the Government Digital Service (GDS). The services represent the 25 highest volume transactions within the seven biggest Whitehall departments and are due to be rebuilt end-to-end by March 2015.
In October GDS admitted it expects just 20 out of the 25 to be launched by next year's deadline, which leaves 12 new digital services due to be delivered between now and then.
Seven of the exemplars are in 'public' beta, meaning they are available online for real users. However six have yet to be released for use by the public and a further three are still listed as being in the 'alpha' phase of development.
Minister for disabled people, Mark Harper (pictured), said: "Carers provide an invaluable service to people in some of the most vulnerable circumstances in our communities.
"We spend around £2bn on Carer's Allowance and are committing even more in the future. A simpler and quicker online system for claiming the benefit is extremely welcome news for those whose time is overwhelmingly dedicated to looking after others."