Rangers have agreed a 10-year licence agreement with sports retailer JJB Sports worth a minimum of £48m.
David Murray has yet to announce a new manager
The Glasgow club will receive an initial payment of £18m on 7 June, when they launch their new Umbro home kit.
A guaranteed minimum annual royalty of £3m will be received by Rangers in each year of the licence.
Rangers chairman David Murray said: "It will allow for the reduction of the club's debt and enable further investment to be made in the team."
Murray, who had promised a major announcement once his side were out of the Champions League, said the club's facilities would also benefit.
But there is sure to be job losses, with the present Rangers Shop chain, which employs 200 people, likely to close.
Rangers say they "will now enter into a period of consultation with the affected staff".
The agreement will allow JJB, who already have tie-ins with Wigan Athletic and Everton, to retail all Rangers' branded sports and leisurewear in their 439 stores across the UK.
As well as the guaranteed £3m royalties each year, Rangers will also be given additional payments when certain levels of turnover are met by the sports company.
"The arrangement capitalises on our strong current retail trading position and will enhance future revenue streams through greater availability and continuity of the quality and range of Rangers product," added Murray.
Rangers announced net debts of £23.1m in the summer and will, of course, lose the revenue their club shops were generating.
However, Rangers are not yet saying anything about a successor to Alex McLeish as manager.
Former Lyon coach Paul Le Guen is reported to have agreed a two-year contract and an announcement of that could be triggered by confirmation of the latest investment.
McLeish, who took Rangers further in the Champions League than any previous Scottish side before Tuesday's exit in Villarreal, has already announced that he will be standing down at the end of the season.
But, when asked if it was possible he could leave earlier, he has simply replied that "I'm here until someone tells me otherwise".
That appears to leave open the possibility of Le Guen taking charge for the run-in to a disappointing domestic campaign.
Rangers, already out of both cup competitions, lie third, well adrift of leaders Celtic, also behind Hearts, and in danger of missing out on qualification for next season's Champions League.
Fans representative David Edgar believes it is time for Murray to make his intentions clear.
"There's no point in this dragging on now," the Rangers Trust spokesman told BBC Sport.
"Rangers are going to have to give the fans something to invest their season ticket money in sooner rather than later."