Randox, a major provider of Covid-19 tests, made a pre-tax profit of £275m in 2021.
It is among the largest annual profits ever recorded by a Northern Ireland-based business.
The accounts for Randox Holdings cover the period from June 2020 to June 2021.
Between January 2020 and December 2021, the UK's Department of Health awarded 22 contracts to Randox, or its strategic partner, with a maximum value of £777m.
Those Covid testing contracts were investigated by the National Audit Office (NAO) over concerns about lobbying and contracts awarded without competitive tendering.
The NAO concluded that it had "not seen any evidence that the government's contracts with Randox were awarded improperly".
However, it added that the Department of Health "did not document key decisions adequately, disclose ministerial meetings with Randox fully or keep full records of ministerial discussions involving Randox".
The Randox 2021 accounts show that its turnover of £618m was 183% higher than the £218m achieved in the previous 18 month accounting period.
The business made a loss of £12m in the 18 months to June 2020 compared to last year's record profit.
Randox's operating profit margin also improved, rising from 21% to 52%.
The strategic report which accompanies the accounts contains a lengthy section on Covid-19 testing.
It says that "through the enormous effort and commitment of its staff Randox has processed more than 23m gold-standard PCR tests for the National Testing Programme and for international travel".
It adds that since the start of the pandemic the business has built, equipped and staffed 80,000 sq ft of testing facilities in Northern Ireland, Manchester and London along with 50,000 sq ft of support facilities.
It says that throughout the pandemic it responded "rapidly, dynamically and cost-effectively to an ever-changing environment".
The number of employees at the firm rose over the year from 1,398 to 2,112.
The government contracts will likely still be a significant factor in Randox's next set of accounts as the NAO said that by October 2021 the Department of Health had paid the firm £407m.
Randox is owned by Dr Peter Fitzgerald, who founded the business in 1982.
He also owns the 1,200 acre Dundarave estate in north Antrim which he bought in 2014.