Anyone over the age of 55 can call the government's Pension Wise service to get help, or book a face-to face interview.
The number is 030 0330 1001.
The news was welcomed by the National Association of Pension Funds (NAPF). But others said it was only just in time.
"With only 2 weeks to go until the new freedoms go live, it has been a close run thing for the Treasury to get the promised service up and running," said Tom McPhail, a pension expert at Hargreaves Lansdown.
And because of the Easter break, there are now only seven working days before the changes on April 6th.
The service will offer "guidance", not "advice".
It will therefore help retirees plan their pensions, and tell them how to shop around.
But it will not:
Anyone wanting guidance can go to the Pension Wise website.
They will be able to book a telephone conversation with the Pensions Advisory Service, or a face-to-face interview with Citizens Advice.
"Hundreds of thousands of savers will be looking to Pension Wise to help them make sound financial decisions to last them the rest of their lives," said Graham Vidler, director of external affairs at the NAPF.
A phone line to give guidance to people ahead of April's pension reforms has opened, just two weeks before the changes take effect.