Goodwill on Incorporation - PYA ?

We have picked up a new client which is a limited company, incorporated 3 years ago. Before the business was incorporated it ran as a two partner partnership. The previous accountant took no account of the goodwill generated by the original partnership when he incorporated it ( simply transferred the tangible assets and liabilities ) . The original partnership was very successful and the goodwill must have been in the region of £200,000 ( my estimate - I know it would require a professional valuation). My question is, at this late stage could we value the goodwill and treat it as a prior year adjustment in the accounts or have we "missed the boat" ?

Any comments welcome. Thanks in advance.