(Adds details on review, penalties, analyst comment, updates stock price, paragraphs 2, 5-12)
TORONTO/LONDON, March 21 (Reuters) - Canada's First Quantum Minerals on Wednesday was hopeful of resolving a dispute with Zambia over a whopping 76.5 billion Zambian kwacha ($8.07 billion) bill for unpaid duties on imported mining equipment.
Zambia has reduced "significant" tax assessments against it in the past, Chief Executive Philip Pascall said on a conference call with analysts. He declined to speculate on the possible outcome of Zambia's review of the latest claim, which involves more than 23,000 documents and could take up to six months.
The bill comprises $150 million in higher import duties, $2.1 billion in penalties and $5.7 billion in interest, First Quantum said. It relates to $540 million in mining equipment imported to its Sentinel copper mine between 2012 and 2017.
"We have, in the past, seen assessments that were significant and then the settlement might be reduced considerably," Pascall said. "In this context, it's not prudent for us try and speculate."
The company's preliminary review of assessment documents, which require approval by the Zambian Revenue Authority (ZRA) before imports are released, show an erroneous application of both higher and lower duties than appropriate, Pascall said.
It was unclear how Zambia calculated the $2.1 billion penalty, First Quantum said, noting that smuggled goods tend to get a 300-percent penalty for customs avoidance, while simple errors typically get a 15-percent penalty.
"This is clearly an eye-watering amount," Bernstein analyst Paul Gait said in a note to clients, comparing the $8-billion bill to First Quantum's market capitalization on Wednesday morning of about $9.5 billion.
"If anything like these claims is actually enforced, it will make Zambia largely uninvestable for any mining company, and probably any other industry as well," Gait said.
First Quantum, which has paid a cumulative $3 billion in taxes to Zambia, said it was unaware why the matter was made public, an unusual move for Zambia. The company's two copper mines in Zambia are unaffected by the issue.
Zambia, which collected 39.1 billion kwacha in taxes last year, netted 4.4 billion kwacha in hidden assets from small companies after they were offered amnesty for such declarations. Dozens of mining companies operate in Zambia, primarily extracting copper.
The Zambian Revenue Authority said it had started detailed audits on all companies for compliance, suggesting other miners may come under scrutiny.
First Quantum shares dipped nearly 2 percent on Wednesday to C$17.68. Shares sank 12.4 percent in Toronto on Tuesday before trading in the stock was suspended.
($1 = 9.4810 Zambian kwachas) (Reporting by Susan Taylor in TORONTO and Zandi Shabalala in LONDON; Editing by Tom Brown and Bernadette Baum)