The deal is part of Trinity鈥檚 ongoing strategy to branch out into other media businesses in order to complement its press offering.
Trinity Mirror will pay an additional 拢2.6m on top of the inital 拢10.45m, depending on performance.
Gaapweb.com was launched in the late-1990s and has established a strong presence in the accountancy and financial recruitment arena.
The site is expected to benefit from cross-promotion from Trinity Mirror鈥檚 regional and national titles, including the Daily Mirror and Sunday Mirror.
Sly Bailey, chief executive of Trinity Mirror, said: 鈥淒igital is a key driver of our growth strategy and recruitment is an important pillar of our advertising revenue, which makes GAAPweb a perfect fit for Trinity Mirror.
鈥淥ur strategy is a careful mix of organic and M&A opportunities which so far this year has seen the launch of 17 new magazines, newspapers and online services and two important acquisitions.鈥
Mark Wainwright, director and joint-founder of Financial Jobs Online, added: 鈥淲e are delighted to be part the UK's largest newspaper publishing group and the benefits that will bring in terms of reach, which will enable the business to grow further.鈥
By Kevin May