That depends on it you are purchasing a company without any fixed assets. If you are just buying the company without fixed assets, made a journal entry. Line 1) Debit Investment in ABC, Inc (an asset account) $65K. Line 2) Credit Owner's equity for $40K. Line 3) Credit Note Payable $25K (a liability account).
If the company has fixed asset, you need to determine the value of the fixed assets. The recording of the entry is a bit different. Line 1) Credit fixed assets (let's say $10k). Line 2) Credit Owner's Equity $40K. Line 3) Credit note payable $25K. Line 4) Debit Goodwill (an asset account) for $55K.
You can amortize Goodwill. Consult your tax preparer.