For the last few years, companies like Google, eBay’s PayPal and Facebook have dabbled in peer-to-peer payments, the business of letting people freely send money to one another through email or on their smartphones. None of these companies have found a way to make money from it.

Square, the e-commerce start-up, is trying to change that.

On Monday, Square will begin allowing businesses to accept payments using Square Cash, the company’s free peer-to-peer payments app, and will charge small-business owners a 1.5 percent processing fee to do so.

The move contrasts with other companies. Peer-to-peer payment apps like Venmo, owned by PayPal, have typically levied no fees, sacrificing revenue for the chance to bolster their user bases. As eBay Chief Executive John Donahoe recently noted, Venmo is highly popular with young audiences, yet brings in no money.

Square Cash will still be free for consumers to use. The company believe its low transaction fee will entice businesses to accept and promote Cash, as it is below the 2 to 3 percent fees businesses must pay for processing credit and debit transactions.

It is a new direction for Square Cash, which until now has only been used for money transfers. Square contends that Cash has been a quiet powerhouse since it was launched a year and a half ago; the company said it processes more than $1 billion in Square Cash transactions on an annualized basis. That, the company said, will only increase the likelihood of the form of payment catching on with businesses.

“The strength of the peer-to-peer network increases the utility of what we’re doing here,” Brian Grassadonia, leader of the Square Cash project, said in an interview.

Square will let businesses accept Square Cash payments through the use of what it calls a “$Cashtag,” essentially a handle and web page that a person or a business can use to accept payments. Each $Cashtag has a unique URL and web page assigned to it, essentially acting as a virtual cash register to which people can send payments.

So for example, a record store that has claimed the identifier $RecordStore can accept payments through its Cash.me address, after a user types debit card information into the web page. Users can also send money to the business through the Square Cash app by using the $Cashtag.

Though Mr. Grassadonia would not detail how much money the company will make on each Square Cash transaction accepted by businesses, he said the company has worked to create a cost structure that makes sense for the overall business.

That would add to the other ways Square currently makes money. Along with regularly processing billions of dollars in credit card transactions, the company also offers a capital extension service, and charges fees for other small-business services like food delivery and scheduling.