What happened

The market may have faced some major headwinds in 2018 as the S&P 500 fell about 6%. But some stocks bucked this trend and delivered returns for investors that were not just good but outstanding. One of these stocks was financial technology company Square (NYSE:SQ).

Square stock soared 61.8% in 2018, according to data provided by S&P Global Market Intelligence. The stock's gain came as Square saw its year-over-year revenue growth accelerate in every quarter reported during 2018.

Square tablet stand and a contactless chip reader device

Image source: Square.

So what

Square saw surging growth in 2018, with the rates surpassing the levels seen in 2017. Revenue and adjusted revenue in the fourth quarter of 2017 increased 33% and 45% year over year, respectively. Comparatively, in the company's third quarter of 2018, revenue and adjusted revenue saw 51% and 68% year-over-year growth, respectively.

Square also notably made significant progress toward becoming a profitable business recently. The company's adjusted EBITDA margin was 16% in its quarter of 2018, up from 13% in the year-ago quarter.

The strength in Square's business comes as the company gains momentum with larger sellers -- those with $125,000 or more in sales. In the third quarter of 2018, gross payment volume from larger sellers was up 41% year over year, accounting for more than half of Square's total gross payment volume.

Now what

Square has yet to provide guidance for 2019, but the company's recent trend of accelerating revenue growth suggests it is poised to deliver more of the same this year. For the full year of 2018, which Square hasn't reported results for yet, management expects adjusted revenue to be between $1.52 billion and $1.54 billion, representing 55% year-over-year growth.

Check out the latest Square earnings call transcript.