Imagine finding more than $700,000 under your couch cushions. That, essentially, is what happened to a man in South Carolina who received a phone call from the state treasurer, Curtis Loftis, informing him that he was entitled to more than $763,000 in unclaimed cash.

This money had belonged to the man’s father, who died more than 15 years ago. The man, who chose to remain anonymous, initially thought the caller was trying to engage him in a scam, Mr. Loftis said.

“I’m so happy that we are able to return the money to the rightful heir,” he said in a statement.

Follow this thread: The man’s mother remarried after his father died. Because of confusion about the son’s surname, the money was never sent to him. Instead, it sat around in a lawyer’s office, before eventually being sent to Mr. Loftis’s office, which then set out to track down the recipient.

“No one on the planet believes that they have money waiting for them,” Mr. Loftis said in an interview in which he recounted the steps he took to track the man down

To find him, Mr. Loftis, who is also the president of the National Association of Unclaimed Property Administrators, found another relative that had passed away in South Carolina. The man’s last name appeared on that relative’s tombstone. Mr. Loftis then used Facebook to find the son of the man Mr. Loftis was looking for. The son told his father, who then skeptically called Mr. Loftis. It took multiple conversations to convince the man that this was real. Mr. Loftis even offered to drive to a Starbucks to meet him in public to prove it wasn’t a scam.

As it turns out, there are boatloads of dollars in unclaimed money given to states every year. South Carolina, for example, has more than $500 million waiting to be claimed. New York has more than $14.5 billion, while California is at $8.4 billion. In total, the United States possesses $43 billion in this type of money.

It comes from sources as varied as inactive bank accounts and uncashed checks to neglected utility deposits. The money might result from clerical errors, botched mail deliveries or just the wrong address on file.

“The most typical example is when people move around, and they haven’t let their bank know what their new address is,” said Thomas DiNapoli, the New York State comptroller.

Another common source is life insurance. In California, for example, Betty Yee, the state’s controller, said there were hundreds of millions of dollars in life insurance benefits still waiting to be claimed because many families don’t discuss the topic.

“It’s not an everyday conversation that you have,” Ms. Yee said.

There is a growing effort by states to try and return the money to its rightful owners. In fiscal year 2015, according to the unclaimed property administrators association, state governments returned roughly $3 billion of the $7 billion it had collected in that year.

We imagine you have some questions.

Am I owed any money?

Almost every state has a program to give back unclaimed money. To find out if you are owed any, go to your state government’s website for unclaimed money, and search. It is typically as easy as simply typing in your name, such as in New York, South Carolina and California.

“You have about a one in four chance of having unclaimed property,” Mr. Loftis said.

In fact, before his interview, Mr. Loftis looked up this New York Times reporter. It turns out that when he typed in “Sopan Deb” of New York into a national database, 11 results came up. Yes, this reporter might have somewhere to look other than couch cushions.

What if I’ve worked in another state?

Check this site out. Missing Money is a national database that aims to be a one-stop shop to search the entire country for money that might be yours. Almost every state has taken part.

“There are organizations who do this for a fee,” Mr. Loftis said. “But you can do it yourself. It’s just that simple.”

These organizations are typically referred to as finders, and they will inform people of their unclaimed funds and then try to take a cut of it in exchange for the convenience of retrieving the money on their behalf.

“We always tell people if you get a call or a letter like that, ignore it because there’s no charge,” Mr. DiNapoli said.

Is there an expiration date on collecting the money?

No.

Mr. Loftis said that the government takes in money from holders, which are entities that hold money not belonging to them. This could include banks, cable companies or a law firm. They might retain payroll checks or bank deposits that went awry.

But once the money is sent to the government, it tries to find the owners to inform them that this money exists.

And it’s not like state governments keep all the money on hand. For example, New York’s $14.5 billion isn’t sitting in an account somewhere.

“Technically, if everybody came out of the woodwork tomorrow and claimed this money, we’d be responsible for the $14.5 billion,” Mr. DiNapoli said. “The reality is some of this money goes back decades and will never be claimed.”

Mr. Loftis said that treasuries keep a “responsible” amount of cash on hand to meet claims as they come in.

$763,000 is a lot of money. Is that typical?

No, although Mr. Loftis said he is chasing the owners of a closed textile mill in South Carolina who are owed $985,000.

“Most of the claims are a hundred bucks or something like that,” Mr. Loftis said. “If it doesn’t mean anything to you, I bet you your church or synagogue would like it, so pick up that money and send it to them.”

In 2008, New York gave a man $4 million for a stock claim.

“Our motto on this is, it’s your money and we’re doing everything we can to make it easy to get it returned to you,” Mr. DiNapoli said.