Relatives of missing people will be able to have them declared "presumed dead" from October, Justice Secretary Chris Grayling said.
Ministers had been criticised for delays in bringing into force legislation passed in March last year designed to help families resolve legal affairs.
The Presumption of Death Act was the result of a campaign supported by relatives of high profile missing people including chef Claudia Lawrence, who disappeared in York in 2009, and Manic Street Preachers guitarist Richey Edwards, who went missing in 1995.
Mr Grayling told the Justice Select Committee that the law - which means a certificate of presumed death can be issued seven years after someone goes missing - would be applied on October 1.
"It is bad enough losing a loved one," he said.
"But losing a loved one without really knowing what has happened is a terrible thing to have to go through, and I hope that this will at least ease some of those burdens."
A promised consultation will begin shortly, he added, on calls from campaigners for a change in the law on guardianship, allowing families to maintain a missing person's estate during these years by cancelling direct debits, paying off debts, and providing maintenance for dependants.
Tory MP John Glen, who introduced the legislation as a private member's Bill, said he was delighted.
"Since I took the Bill through the Commons, I have had a number of individuals contact me, who were often in tragic circumstances and trying to move on with their lives after losing a loved one," he said.
"It was unacceptable that families had to wait seven years before they could get a presumption of death certificate and ensure their affairs were in order.
"I hope Presumption of Death certificates will make this process easier when someone goes missing, and ease some of the burden on those who are left behind."
Peter Lawrence, Claudia Lawrence's father, said: "I am very pleased that, after a long delay since March 2013 when the Presumption of Death Act was passed in parliament and received royal assent, it is finally going to come into force on October 1 and thus be able to be utilised by the many that are waiting to use its powers.
"It is also good to hear that a consultation on guardianship is to take place soon and it too needs to become law as soon as possible afterwards to enable the many thousands of families who would wish to use this within a short period after their loved one has gone missing and enable them to keep the person's affairs in order in their absence."