Mattioli acquired a 49% stake in the small-cap boutique in February 2017 and had a two-year window in which to buy the remaining 51% of shares.
The wealth manager and employee benefit specialist announced earlier this year it had agreed to cancel the option in exchange for a £750,000 payment from the management team.
Since Mattioli snapped up half of the business, Amati has seen its funds under management more than triple, growing from £120m to £430m.
The sole Oeic fund in its stable, TB Amati UK Smaller Companies, has been rated by research houses Morningstar, RSM and FE Analytics. It is in the second quartile of funds in the IA UK Smaller Companies sector over one year and in the first quartile over three and five years.
Mattioli Woods chief executive Ian Mattioli (pictured) called Amati “an excellent fund manager” and praised the business for “growing well and sustainably in difficult markets”.
As part of the agreement Mattioli has said Amati should maintain its policy of giving 10% of profits to charities registered in the UK in the future.
Total assets at Mattioli hit £8.8bn at the end of last November. Like others in the wealth management space it reported staff cuts last year.
Shares in the wealth manager have risen 20% year-to-date to 796p.