Kogan's shares were hammered down by more than 30 percent on Monday after revealing the cost of changes to Australia's GST laws.
The online retailer's share price fell from $4.64 each at the end of trading last week to $3.08 at the time of writing, representing a 34 percent decline.
The drop in share price reflects a business update Kogan issued on Monday morning, which revealed that revenue from the "global brands" category had decreased by 27.4 percent in the most recent quarter.
At the same time, revenue from exclusive brands grew 15.7 percent, while partner brand sales grew 73 percent, which Kogan said was likely driven by on-boarding new brands and some customers transitioning away from global brands.
The bulk of the blame was placed on the introduction of new GST laws on 1 July, which abolished the GST threshold on imported goods worth more than $1000.
"Initially, this saw some competitors exit the market and the company's July revenue grew 33 percent year-on-year," Kogan said in a statement to the ASX.
However, the company said "widespread avoidance of GST has become apparent" and that competition from foreign websites that sell into Australia without GST was eroding its gross margin.
"At this stage, the company is unable to determine whether the recent widespread avoidance of GST will be temporary."
Founder and chief executive Ruslan Kogan said the company would continue its long-term strategy of growing its ecommerce footprint.
"While growth in the global brands division presents a challenge to the business in the short term, we have built a resilient portfolio of businesses, with the core divisions of exclusive brands, partner brands and Kogan Mobile continuing to show healthy growth."
Kogan also revealed in the business update that it was pulled up by the ACCC in October over some of its marketing and pricing promotions it ran in June. Kogan said it was in the process of compiling information for the consumer watchdog.
Kogan's shares were already sent down last month when its two founders sold off approximately $40 million in company shares, which was soon met with a nine percent drop in share price. It marked the second time Kogan's founders sold off millions in personal shares, having offloaded six million shares that were valued at $42 million in June.
The company's share price hit an all-time high in March this year of $9.85 each.