About 650 jobs are to be cut at the newly formed bookmaking giant Paddy Power Betfair.
Two months on from the creation of the massive betting business, staff in offices across the UK and Ireland were being told of the redundancies.
Bookmaking shops will not be affected but jobs are expected go in the legal, human resources, finance, technology and trading divisions as the company reduces duplication across its 7,000-plus workforce.
It is understood 350 jobs will go from the UK operations and about 300 from the Irish end of the business.
Two main offices will be created in Clonskeagh, Dublin, where "Power Tower" has been based for several years, and in a second centre in Hammersmith, London.
Paddy Power Betfair was created when a £5 billion merger was finalised in February.
The mega-deal left the bookmaking chain with 336 shops in the UK and 252 stores in Ireland as well as a huge online betting operation.
It posted pre-tax profits of 179.7 million euro (£139.1 million) in the year to the end of December.
The massive tie-up was announced amid growing consolidation in the industry. It followed hot on the heels of an agreed £2.3 billion merger between Ladbrokes and Gala Coral last July, with bwin.party spurning 888 holdings in favour of a £1.1 billion cash-and-shares offer from Sportingbet owner GVC.
While the company declined to comment on the job cuts, government officials in Dublin were informed on Monday as management began the process of notifying staff.