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Crossrail will be completed two years behind schedule, transport bosses have admitted.
But the completion between October 2020 and March 2021 will not include the opening of Bond Street, one of 10 new stations along the new Elizabeth Line, they said.
London mayor Sadiq Khan described the new timetable as "realistic and deliverable".
The new £17.6bn railway across London was due to open last December.
"Many risks and uncertainties remain in the development and testing of the train and signalling systems," Crossrail Ltd said in a statement, having identified a new "six-month delivery window" for the project.
The line had been rescheduled to open this autumn but that had been cast into doubt after further setbacks were reported.
Crossrail said Bond Street's opening had been delayed "because of design and delivery challenges" and would be unveiled "at the earliest opportunity".
Its chief executive Mark Wild told the BBC's Today programme Tottenham Court Road station would be open and he hoped Bond Street station would be opened soon after the Elizabeth Line started operating.
"It's very disappointing we didn't make it in December but we've got a plan now, a clear plan, to get it opened by the end of next year.
"I think the project in the summer of last year got itself into quite a compressed state with overlapping activities."
He added: "My job now is to get the railway open."
Crossrail said it had major tasks to complete before opening the line, including creating and testing software that would integrate the train operating system with three different signalling systems.
It said it also needed to finish installing equipment in tunnels, test communications, install and test station systems and trial run the trains over many thousands of miles on the completed railway.
Mr Khan said the new Crossrail leadership team had worked hard to "establish a realistic and deliverable schedule for the opening of the project, which TfL and the Department for Transport will now review".
The London Assembly Transport Committee has welcomed the announcement with "cautionary relief", its chair Caroline Pidgeon said.
However, she also said: "The project has been pushed back twice already, so the question has to be asked, 'Is the six-month window a hedge-betting exercise to avoid disappointing passengers once more?'
"It is also incredibly frustrating that no senior executives will accept any responsibility for the litany of failures that have led to this delay."
Three emergency cash injections have seen the cost of the project rise from £14.8bn to £17.6bn.
Source: BBC