If you were a consumer in Slovakia, would you submit your purchasing receipts to the government in hopes of winning a car in a lottery knowing that the government are using the receipts to detect business tax cheats?

When Jozef Lazarcik, a 35-year-old factory worker, heard his number called on national television here recently, he pumped his fists, hardly believing his luck.

He had registered only nine receipts with Slovakia’s new tax lottery, and yet he had just won a new car. “It’s a heavenly feeling,” he said before leaving the studio, ready to encourage all of his friends to register their receipts, too — which is exactly what Slovakian officials were hoping for.

Over the last 10 years, Slovakia’s revenue from value-added taxes, a type of sales tax, has declined. But hiring auditors and pursuing individual merchants and service providers in court is expensive and slow. So last fall, the government decided to put a lottery in the mix.

The idea is to enlist average citizens to collect receipts from their purchases and register them with the government, creating a paper trail for transactions and forcing restaurant and shop owners to pay the sales taxes they owe. As Slovakians register their receipts for the lottery, a computer will also tell them if a merchant has issued a receipt with a fake tax identification number, so they can report suspected fraud.

For any purchase worth more than 1 euro, or about $1.38, Slovakians can enter their receipts in a monthly lottery to win €10,000, a car or a chance to be a contestant on the Slovakian version of “The Price Is Right.”

Tax officials say the lottery is already having a big impact, and other European countries that are also struggling with the collection of value-added taxes have considered it — including Portugal, which started its own tax lottery on Thursday. In Slovakia, about 450,000 people have taken part, registering about 60 million receipts, officials said.

Complaints about merchants who will not give receipts have skyrocketed. In the six months before the lottery began, the government received about 300 such complaints, officials said. In the first few months after it started, that number rose to 7,000.

“It has been a huge success so far,” said Peter Kazimir, Slovakia’s finance minister.

Value-added taxes are an important source of income for European countries, but collecting them has grown more and more difficult during the economic crisis. A recent report for the European Commission found that uncollected value-added taxes in the European Union — a measure known as the value-added tax gap — amounted to about $267 billion in 2011. Across the bloc, that gap increased by five percentage points on average since the onset of the debt crisis in 2008.

But for some countries — especially Greece, Ireland, Latvia, Portugal, Slovakia and Spain — the problem has been particularly acute. A decade ago, Slovakia was able to collect about 80 percent of taxes due, said Peter Golias, the director of Ineko, a nonprofit economic research group here. That figure is now about 60 percent, putting Slovakia in a league with Greece for the poorest record on the collection of value-added taxes.

Mr. Golias said some people had been inspired to play the lottery because they were tired of tax cheats. “They really want to help,” he said.

For others, it is more about winning. Sylvia Skanderova’s father once won about $11,000 in a lottery. That has made him an eager participant in lotteries of all kinds, she said, but particularly this one, because it costs nothing to play. He spends three hours every Sunday registering receipts.

“The neighbors, they know my father does this, so they bring him receipts,” said Ms. Skanderova, 26. “Every Sunday his eyes are bloodshot. We have huge plastic bags in the basement with receipts.”

Zuzana Candikova, a manager at Planetka Restaurant here in Bratislava, the capital, is hoping to win a cash prize that she would use to help buy an apartment. She collects receipts that her customers leave behind, but she has a friend who does the registering. If they win anything, they will split it, Ms. Candikova said.

The lottery is not Slovakia’s only push to increase its tax collection. In the last few years, under pressure from the European Union to improve its finances and attack corruption, the government has also run a “name and shame” campaign against tax cheats, raised the salaries of tax inspectors and stopped political appointments in the tax office, among other measures.

Tax collection began to increase early in 2013 and rose more sharply after the lottery began. Officials say they collected about $512 million more in 2013 than in 2012. How much of that is a result of the lottery may never be clear.

But Mr. Kazimir said that it was surely a big factor, and that it had cost only about $276,000 to get the lottery going. He said the new influx of complaints had already proved that it was not just small businesses that were cheating: Chain stores have also been caught giving fake receipts.

In Portugal, too, the value-added tax gap has grown since the start of the economic crisis. Having asked for a bailout of about $108 billion in 2011, it is under pressure from its creditors to do better.

Portuguese officials believe their tax lottery will be especially effective because gambling is popular among Portugal’s 10 million inhabitants, who are already among the biggest participants, in terms of spending per capita, in the EuroMillions lottery shared by nine European countries. Over the past decade, the Portuguese have spent an average of about $1.2 billion a year on EuroMillions.

Paulo Núncio, the Portuguese secretary of state for tax affairs, said the government was counting on the new lottery to raise its tax revenue by about $830 million to $1.1 billion.

Even before the start of the Portuguese tax lottery, it was generating excitement. In the food court of the Amoreiras shopping mall in Lisbon recently, customers ordering hamburgers joked that their lunch order could result in a new car.

The lottery project has drawn criticism from some Portuguese opposition politicians who say it is a capitalist tool to turn citizens into tax inspectors.

Diogo Ortigão Ramos, a partner at the law firm Cuatrecasas, Gonçalves Pereira in Lisbon, said the lottery also raised “questions of compatibility with E.U. law.” For the time being, though, the European Commission has not addressed this issue.

Portuguese merchants say they have already seen a change. João Raposo, a restaurant owner, said customers were increasingly asking for a full tax receipt, when “five years ago nobody would have bothered.”

If you were a General Mills executive, would you change a new policy that required consumers to use arbitration rather than lawsuits to settle disputes because of complaints on Facebook and Twitter? 

General Mills, one of the country’s largest food companies, on Saturday night announced in a stunning about-face that it was withdrawing its controversial plans to make consumers give up their right to sue it.

In an email sent after 10 p.m. on Saturday, the company said that due to concerns that its plans to require consumers to agree to informal negotiation or arbitration had raised among the public, it was taking down the new terms it had posted on its website.

“Because our concerns and intentions were widely misunderstood, causing concerns among our consumers, we’ve decided to change them back to what they were,” Mike Siemienas, a company spokesman, wrote in the email. “As a result, the recently updated legal terms are being removed from our websites, and we are announcing today that we have reverted back to our prior legal terms, which contain no mention of arbitration.”

The announcement was a stunning reversal for the company, which had quietly put up the new terms requiring consumers downloading coupons, “joining its online communities,” participating in sweepstakes and other promotions, and interacting with General Mills in a variety of other ways to agree to arbitration in lieu of suing the company in the event of a dispute.

Those terms, which were first reported by The New York Times on Wednesday, were widely excoriated by consumers on Facebook and Twitter, and legal experts questioned whether the broad language the company used could be enforced. In a pop-up box on its home page, the company had said it would “require all disputes related to the purchase or use of any General Mills product or service to be resolved through binding arbitration.”

The company elaborated on its change of heart in a blog post.

If you were a Michael’s executive, how would you deal with customers and credit card companies after announcing that hackers obtained 3 million customer payment cards data?

Michaels Stores, the arts and crafts retailer, estimates that data on three million of its customers’ payment cards may have been stolen in a breach over several months.

Michaels first acknowledged that it was investigating a possible breach in January, not long after it was revealed that Target experienced one of the largest recorded data breaches in history, affecting about 100 million customers.

Several other retailers and a hotel company have since disclosed similar breaches that have put the online security of consumers and cybercrime under scrutiny.

In a statement posted on its website late Thursday, Michaels said that two security firms had found evidence of a breach at Michaels and at a subsidiary, Aaron Brothers, a framing company. The computer hack involved “highly sophisticated malware that had not been encountered previously by either of the security firms,” the company said.

Like the Target breach, the attack at Michaels invaded its point-of-sale systems. There are more than 1,135 Michaels stores and 119 Aaron Brothers locations, and the company has posted two long lists of branches that were affected on its website.

“In an era where very sophisticated and determined criminals have proven capable of successfully attacking a wide range of computer networks, we must all increase our level of vigilance,” Chuck Rubin, chief executive of Michaels, said in a statement.

The retailer said that its systems were exposed at various Michaels stores in the United States from May 8, 2013, to Jan. 27, 2014, exposing information like credit and debit card numbers and expiration dates. At this point, the company said it believed that personal information like names and addresses had not been hacked. About 2.6 million cards may have been revealed to hackers during that time, or about 7 percent of the cards used at Michaels stores in the United States over those nine months.

At Aaron Brothers, which sells custom frames and art supplies, 400,000 customer cards may have been exposed, the company said. Its systems were compromised at 54 stores from June 26, 2013, to Feb. 27, 2014 — more than a month after the company said publicly that it may have been hacked.

The data breaches at Michaels and Target, as well as at Neiman Marcus, were believed to be committed by a loose band of criminals in Eastern Europe.

The fallout from these hackings has been widespread and has affected many millions of people whose personal or payment data has been exposed.

At Target, which experienced by far the worst of the recent breaches, its fourth-quarter profit was down 46 percent from the period a year earlier, and executives said there was a significant decline in traffic and sales after the breach became public. Last month, the company’s highest-ranking technology executive, Beth M. Jacob, resigned. And John J. Mulligan, Target’s chief financial officer, has testified before Senate panels, along with an executive from Neiman Marcus, and others.

Some banks have reissued credit and debit cards with new numbers after learning that their customers had become vulnerable by shopping at those stores.

Eager to keep a widespread theft from happening again, retailers and trade groups have been calling for a swift transition to a payment card technology, widely used in Europe and considered more secure, called EMV, which relies on a small chip embedded in each card rather than a magnetic strip.

This week, the National Retail Federation announced that it would create a platform through which retailers could obtain and share information on online security threats. Little information was exchanged among some of the companies in the past.

“Establishing a new program takes time,” Matthew Shay, president of the federation, said in a statement, “but time is not our friend when it comes to stopping these sophisticated and unpredictable criminals.”

If you were a college president would you ban the use of cellphones for taking selfies at graduation when students receive their diplomas? What would you do if a student defies the ban?

Sign of the times: Bryant University in Rhode Island has told its graduating seniors not to take selfies when they come onstage for their diplomas next month.

“We have about 850 graduates, and we have a professional photographer snapping their picture when they shake my hand and get their diploma,” said Ronald Machtley, the president of Bryant. “I don’t think their mom and dad and grandma want to get a picture of them holding up their cellphone.”

Last year, some graduates used their phones to take pictures of their big moment, and the commencement committee worried that this year everyone would do the same, slowing down the ceremony.

This is hardly a war on social media, however. While the parents are waiting for the ceremony to begin, students will be encouraged to post messages — “Thanks, Mom and Dad” was suggested — to an online tagboard that will aggregate them using the Bryant graduation hashtag.

And when the president and his wife welcome the graduating class to their home in the lead-up to commencement, there will be plenty of time for selfies. “I’ll stand there with anyone who wants one,” the president said.

Mr. Machtley, a major user of social media, counts 2,200 of Bryant’s 3,300 students among his Twitter followers. The no-selfie policy was issued via the app Snapchat.