Jerusalem for a previously announced fresh questioning as part of an inquiry underway known as Case 4000 or Bezeq.
A final case, dubbed 3000, is being investigated separately and has involved Netanyahu allies, but the prime minister has not been named as a suspect.
Israeli Prime Minister Benjamin Netanyahu speaks during the Muni World conference in Tel Aviv, Feb. 14, 2018. Police, however, confirmed that it was "being carried out with the supervision of the state attorney and approval of the attorney general".
Police have not yet called for an indictment in this case.
However, Netanyahu denies any wrongdoing and charges the allegations are part of a witch-hunt by the media and "the left".
Shlomo Filber, a Netanyahu ally for more than 20 years and former director general of the communications ministry, was freed last week after agreeing to turn state's witness in exchange for avoiding jail, police said.
Justice Minister Ayelet Shaked, a member of the ultranationalist party Jewish Home, said that according to the law, Netanyahu can stay in the job through the end of his trial. That decision could be weeks or months away.
In Case 1000, Netanyahu and his wife are suspected of receiving illicit gifts from billionaire benefactors, amounting to some NIS 1 million ($282,000) worth of cigars and champagne from the Israeli-born Hollywood producer Arnon Milchan and Australian resort owner James Packer in return for certain benefits.
Sara Netanyahu was expected to give a statement about her ties with Shaul Elovitch's wife, Iris, and the messages that she is suspected of having relayed to her about Bezeq and coverage of the Netanyahus on the Walla website, Israel radio reported. In return, police say Netanyahu operated on Milchan's behalf on USA visa matters, legislated a tax break and connected him with an Indian businessman.
In the other case, Netanyahu is accused of offering a newspaper publisher legislation that would weaken his paper's main rival in return for more favorable coverage.
So far, partners in Mr Netanyahu's governing coalition have stood by him, saying that they are awaiting the next moves by the Attorney-General. In the meantime, Netanyahu is not obligated to resign and has indicated he will fight the charges while remaining in office.
Television footage showed police investigators entering Mr. Netanyahu's residence.