The Nobel peace laureate, who died last December, left several assets to his third wife on condition she forfeited her right to half the USD 4.3 million estate.
"I confirm that Mrs Machel has formally and in writing accepted the benefits bequeathed to her in the last will and testament of former president Mr NR Mandela," executor Dikgang Moseneke told Sapa news agency.
Mandela and Machel had been married for 15 years "in community of property", which under South African law meant she had the right to half his estate.
South Africa's first black president left money to his children and grandchildren, donations to educational institutions he attended and to his party the African National Congress.
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Mandela spent 27 years in jail before becoming head of state after the first all-race elections in 1994 and his politics of forgiveness and reconciliation made him a global peace icon.
He married Machel, the widow of Mozambique president Samora Machel, in 1998.
Mandela died on December 5 and was buried 10 days after in his rural boyhood home of Qunu after a state memorial service attended by dignitaries from around the world.