The outcome of an SPL-appointed commission's inquiry was announced on Thursday.
Its chairman, Lord Nimmo Smith, ruled that Rangers oldco had failed to correctly register players in the period between 2000 and 2011, and would be fined £250,000.
However the five league titles they won during that time would not be taken away.
The fine will be payable by the former owners of Rangers rather than the Charles Green's newco, which took over in July 2012.
The three-man commission reached a unanimous verdict on the matter.
It found that Rangers, under Sir David Murray's stewardship entered into side-letter arrangements with a large number of players, with the club making payments to an offshore Employee Benefit Trust (EBT) and payments made to players in the form of loans.
These were not disclosed to the Scottish Football Association, a statement said.
It added that a "substantial" financial penalty would be imposed, but the most severe sanction of taking away titles wouldn't - as the club hadn't gained "an unfair advantage".
The comission continued: "Although the payments in this case were not themselves irregular and were not in breach of SPL or SFA Rules, the scale and extent of the proven contraventions of the disclosure rules require a substantial penalty to be imposed.
"Rangers FC did not gain any unfair competitive advantage from the contraventions of the SPL rules in failing to make proper disclosure of the side-letter arrangements, nor did the non-disclosure have the effect that any of the registered players were ineligible to play, and for this and other reasons no sporting sanction or penalty should be imposed upon Rangers FC.
"In all the circumstances the commission has imposed a fine of £250,000 on Oldco."