The firm, which has 2,362 betting shops, took the hit when all the favourites in the Premier League won on the middle weekend in January apart from Manchester City.
It added that this one loss-making week of customer-friendly football results had left it behind on its internal expectations to date.
The business, which also runs operations in Australia, the US and Europe, said pre-tax profits for last year fell 9 per cent to £233.9m following a number of other adverse results as well as £83.4m of exceptional charges largely relating to an earlier acquisition.
The firm said it had a record World Cup, generating £226.8m of bets and added that comparisons were impacted by favourable results a year earlier.
Despite the tough start, William Hill said it remained confident of meeting its full-year expectations in 2015.
Earlier this month William Hill’s £709m bid to buy online rival 888 collapsed because it could not agree a price with its major shareholders.
The gaming sector is facing pressure over controls on betting shops and gaming machines. Shares across the industry slumped last year as bookies were hit with a surprise hike in gaming machine duty in the Budget.
The business said it closed 108 shops in the year and opened 52, in response to the hike in gaming machine duty to 25 per cent on 1 March.
But it added gaming machine revenues were 6 per cent higher at £461.7m over the period as it rolled out its next-generation Eclipse machines to half of its estate by the third quarter of the year. By the end of the year it had rolled out 70 per cent of the machines across its stores.
SUBSCRIBE TO THE SCOTSMAN’S BUSINESS BRIEFING