The final price of the restructuring stood at £55m at the end of the 2006-07 financial year, rather than the £40m that had been forecast by the firm's management.
It is understood that the £15m excess came in the last few weeks before books closed on the financial year, when the magic circle firm saw at least 13 partners leave, including six in London.
Freshfields declined to comment, but The Lawyer understands that until March the firm was on course to keep to its £40m restructuring budget. Severance packages for departing partners in the last month pushed up the costs unexpectedly.
It is understood that these were absorbed in the last set of financial results, in which turnover still rose by 12 per cent to £988m.
The restructuring was part of a profitability drive that saw Freshfields cull 100 partners from the equity over 18 months.
Some left the firm, some were de-equitised and a controversial pension reform last summer saw 30 senior lawyers opt to retire from the equity partnership to benefit from favourable terms from the old unfunded pension.
Freshfields' equity partnership now stands at 420 out of a total partnership of 450.