Financial-technology company Square (NYSE:SQ) has turned a lot of heads on Wall Street. Its stock is up an incredible 100% year to date at the time of this writing -- and that's on top of a 154% gain in 2017.

The favor Square has garnered with investors is unsurprising. The company seems to be doing everything right. It has repeatedly raised its guidance for the full year, and its revenue growth rates have accelerated for four consecutive quarters. In addition, it has been delivering strong, double-digit-percentage growth across each of its business segments.

But how long can it keep up its momentum? While meaningful deceleration in the company's growth is inevitable over the long haul, there's at least one good reason to believe those elevated growth levels could continue at least through 2018: the company's growing traction among larger sellers.

An employee and customer interact with the two displays included with Square Register

A Square Register point of sale system. Image source: Square.

Attracting larger sellers

Square's first product -- a mobile credit card reader -- was aimed directly at small businesses, and to this day, it continues to cater to that market. For instance, though its Square Capital unit has facilitated a total of $2.8 billion loans so far, they've primarily been made to small businesses: The average loan size in the first quarter was only about $6,800. 

But Square is successfully scaling its products and services to address the needs of larger businesses as well. In its most recently reported quarter, adjusted revenue from large sellers -- those that generate more than $125,000 in annualized gross payment volume (GPV) -- increased 60% year over year. Highlighting how large sellers are contributing outsize growth for Square, the company's total adjusted revenue during the period increased 51% year over year.

Similarly, GPV from large sellers in Q1 increased 44% year over year, handily outpacing the 31% growth in overall GPV the company achieved during the period.

At this point, large sellers represent a significant portion of Square's business. In Q1, they accounted for 47% of its total revenue.

Why this trend will likely continue in 2018

It's not just Square's recent strong performance with large sellers that supports the case for that segment to keep providing meaningful growth in 2018. There are several near-term catalysts that could enhance its appeal to those customers.

First, there's Register -- a high-end point-of-sale device that Square debuted late last year. As the company's priciest product, and its first to integrate hardware, point-of-sale software, and payments technology, it's attracting a new type of client to the company's platform. The average GPV of Square Register sellers is $300,000, and a third of the businesses buying the systems are new customers to Square.

Another catalyst that should attract larger sellers to Square is the recent launch of its restaurant platform, which provides solutions for both front- and back-end operations, and is integrated with the rest of the company's ecosystem. Square for Restaurants is a sophisticated product that will appeal to more than just mom-and-pop operations.

A restaraunt employee interacts with Square for Restaurants platform

The Square for Restaurants platform. Image source: Square.

Rapid growth in the number of large sellers using Square's platform is particularly beneficial because they're embracing not just the individual products, but the ecosystem; over half of those customers are using multiple Square products. "As these sellers use more products, we deepen our relationship with them, and they drive meaningful growth for Square," management said in the Q1 letter to shareholders.

Investors will learn more about how Square is faring with large sellers when it reports its Q2 results after market close on Aug. 1.