If confirmed, the news will also heap pressure on Finance Minister Taro Aso who insisted on Friday he had no plans to resign over the affair.
The media reports come after a finance ministry official, who was reportedly at the heart of a scandal over the cut-price sale of government-owned land to a close friend of Abe, was found dead and a second key official stepped down Friday.
The ministry on Monday will report to the parliament that some of the descriptions in the land sale documents were removed before being submitted to MPs, local media said.
The Mainichi Shimbun reported that it was "likely that the documents had been altered to be coherent with" the speech made in parliament by Nobuhisa Sagawa who stepped down as the head of the National Tax Agency over the scandal.
"It is possible that Sagawa instructed the alterations," the newspaper said, citing government sources.
The scandal has dogged Abe since it first emerged last February, though the prime minister has consistently denied any wrongdoing and his approval ratings remain solid with political opposition to him weak.
According to local media, the land was sold for around one tenth of its market value.
The buyers had announced plans to name Abe's wife Akie the honorary principal of a school being built on the same plot.
Abe says his wife had only "reluctantly" accepted the post of honorary principal and had since "resigned."
Earlier this month, allegations emerged that the finance ministry's documents on the sale had been tampered with before being submitted to parliament.
The allegation has paralysed parliament in recent days, with some opposition lawmakers boycotting debates.
The opposition has accused ministry officials of hiding some key documents and colluding to cover up the scandal.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)