(Adds more details, Left comments, updated share move)
TORONTO, Oct 11 (Reuters) - Short-seller Andrew Left of Citron Research said on Wednesday he was investigating various aspects of software company Shopify Inc's business and would "most likely" publish a follow-up to an Oct. 4 report that sent its shares plunging.
"I am looking at many parts of the business," Left told Reuters, adding that his focus included areas not covered by his initial report.
Among other issues, he said he wants Shopify to disclose data on so-called customer churn, or the rate at which clients leave, a key metric to evaluate companies that sell subscription services.
Shopify declined to comment. Chief Executive Tobi Lutke said on Twitter on Tuesday that he would respond to Left's claims on the company's next earnings call, which is expected the week of Oct. 30.
Shares in Shopify, which provides websites, payments and shipping services to some 500,000 online merchants, have dropped more than 18 percent since Left released his original report, shedding more than $2 billion in market value.
The report said Shopify engages in aggressive marketing practices that oversell the potential for its customers to make money.
Shopify, which has yet to turn a profit, issued a statement on Oct. 5 that said, "We vigorously defend our business model and stand resolutely behind our mission and the success of our merchants."
The stock is still up 100 percent so far this year, making it 2017's top performer in the Toronto Stock Exchange composite index.
Some analysts remain enthusiastic about the prospects for its core product, which merchants can use to sell products through the world's largest websites through a single store. Shopify recently added eBay Inc to a list of partners which include Facebook, Amazon.com Inc and Pinterest.
Analysts have also said paying a premium for Shopify shares was worthwhile, since the value of goods sold on its platform is growing at a healthy annual rate of 75 percent.
The stock rose 2.6 percent to $95.02 on Thursday, more than five times its May 2015 initial public offering price of $17.
Even with its recent fall, Shopify's stock is trading at roughly 10 times its expected 2018 sales, significantly higher than peers such as Salesforce.com Inc, which trades at around six times expected sales. (Reporting by Alastair Sharp in Toronto; Editing by Jim Finkle and Tom Brown)