Owner of Guardian Media Group - The Scott Trust - has changed from being a trust to a limited company.
The move comes 72 years after the trust was created with the object of "securing the financial position and editorial independence of the Guardian in perpetuity".
It currently comprises nine trustees, who between them own all the shares in GMG - which owns The Guardian, Observer and a broad portfolio of other media interests including the B2B division of Emap.
Explaining the move, the Scott Trust said today in a statement: "Like all non-charitable trusts, and unlike limited companies, the Scott Trust has a finite lifespan.
"In light of this, the trustees have decided that pursuance of the core purpose is best served by transferring ownership of the shares they currently hold in GMG to a newly formed, permanent limited company, The Scott Trust Limited. This company becomes the new parent of GMG, replacing the existing trust.
"All Scott Trustees become directors of The Scott Trust Limited, with Dame Liz Forgan appointed chair. All shares in the new company are held by current trustees. On completion of the restructuring process the existing Scott Trust will be wound up.
"The change reinforces existing protections for the Guardian. The core purpose has been enshrined in the constitution of The Scott Trust Limited and cannot be altered or amended.
"The new company is not permitted to pay dividends, and its constitution has been carefully drafted to ensure that no individual can ever personally benefit from the arrangements.
"In the unlikely event of its winding up, the assets of the company would be transferred to some other entity which has a similar purpose."
The trust said that the change addresses "the hypothetical risk of future changes in inheritance tax law that could, in theory, threaten the Guardian's independence".