The firm, which is a major employer in Yorkshire with 3,000 staff, including 1,300 in Leeds, said pre-tax profits fell 35 per cent to £78.7m in the six months to the end of June.
The group was also hit by one-off charges relating to its Australian operations.
William Hill said that its half-year results had been dragged down by the effect of the “point of consumption tax” on online gambling as well as the hike in duty on fixed odds betting terminals from 20 per cent to 25 per cent.
It also said profits had been hit by the Machine Games Duty increase, as well as new controls on the way customers who wish to stake more than £50 on gaming machines may bet.
In addition the group said the introduction of the National Living Wage for workers over 25 is expected to cost it £1m to £2m in 2016.
Net revenues were marginally ahead from £805.2m to £808.1m compared with a period last year that included the start of the World Cup. UK online revenues rose 16 per cent.
In a separate announcement, William Hill announced it is moving into the online lotteries market with the acquisition of a 29 per cent stake in US-focused business NeoGames.
The group said its US business continued to deliver strong growth.
Chief executive James Henderson said: “We have delivered a good operational performance in the past six months during a period of significant regulatory and taxation change for the industry.
“Whilst factors such as the Point of Consumption Tax and the increase in the Machine Games Duty rate have impacted our cost base as expected, we continue to progress our strategy and invest in our long-term growth drivers.”
The company said that the UK “remains an exciting growth market”, citing latest data showing National Lottery participation losing ground while betting and online gambling were increasing in popularity.
William Hill, which has 2,360 betting shops in the UK, is set to be overtaken as the country’s largest bookmakers’ network after rivals Ladbrokes and Coral agreed a £2.3bn merger last month.