Although it won't officially launch to the public until 12 December, a test site went up on Friday.
The site has 167,000 entries and works as a search facility providing financial data on charitable organisations while giving them a chance to include their mission statements and other information such as fundraising and targets.
GuideStar has been working with the Charity Commission to set up the site, and admits the regulator might manage it in the future.
Erica Roberts, chief executive of GuideStar UK, said: "It is possible the Charity Commission might pick it up one day." She declined to comment on whether the charity was in discussion with the commission about a possible handover. She said it would cost £1.4m a year to keep the site up to date.
Roberts added that there was a strong case for further Government funding, but has also said that revenue will be raised through selling data to organisations.
The cost of GuideStar UK has been the subject of criticism since its inception. It received £2.9m from the Treasury's Invest to Save Budget and has received more than £1m from other funders, including the Bridge House Trust, the Institute for Philanthropy and the Community Fund.
Critics complained it was an excessive sum to spend on providing access to information already in the public domain.
Roberts said the site had come in under budget and within the three-year timeframe originally set by the Government.