One of UK's top-selling artists, British singer-songwriter Ed Sheeran is facing a lawsuit for €18 million for his hit song Photograph, which according to the lawsuit has 39 identical notes to two California-based musicians’ song Amazing.

The copyright infringement lawsuit was filed on Wednesday by songwriter and producer Martin Harrington and Thomas Leonard, songwriter. They claim Photograph's chorus shares 39 identical notes and a similar structure to Amazing, performed by Matt Cardle.

Amazing was written in 2009 by Harrington and Leonard, while Photograph came out five years later in 2009, according to the lawsuit.

According to the lawsuit, Sheeran stated in a 2014 interview with Nova FM that he thought Photograph "will be the one to change (his), kind of, career path."

The court documents include musical note comparison and chord breakdowns of the two songs, with similarities Harrington and Leonard claim to be "instantly recognizable to the ordinary observer."

Chords in 'Amazing' and 'Photograph' compared in court documents.

Notes of 'Amazing' and 'Photograph' in court documents.

The songwriters seek a jury trial and damages in excess of $20 million, as well as royalties for the song.

Besides Sheeran, other defendants include co-writer Johnny McDaid, of Snow Patrol, as well as Sony/ATV Music Publishing, Warner Music Group and its subsidiary, Atlantic Recording Corporation.

After its release in 2015, Photograph reached no 1 on Billboard US Adult Top 40 Chart, among others. It has sold over 2 million copies in US alone, with more than 280 million views on YouTube. Amazing has just over 1 million views on YouTube.