The value of a software business is largely based on what IPRs it owns. Accordingly, it is crucial to establish what IPRs are material to the business and who owns those IPRs. They can take the form of trade marks (for business names or the names of software products), patents (in the software's functionality), copyright (in the software code), and sometimes database rights and designs. Other rights that are not "intellectual property" in a strict sense, such as domain names and confidential information, are likely to be important to the business too.
It will be easier to identify and check title to registered IPRs than unregistered rights: trade marks and designs may exist as registered or unregistered rights, patents only exist as registered rights, and in the UK and EU (unlike in the US), copyright is not registrable. The buyer will usually conduct searches of trade mark and patent registers for all relevant jurisdictions and a WHOIS database search for domain names.
As well as identifying registered IP, given that material IP in a software business will be copyright and not registered, the seller should be required to list its material unregistered rights. It is important to check that there is a clear chain of title to all material software products. The seller should be required to identify how, when and by whom each key software product was developed and whether the software was developed by external consultants or employees. Unless there are relevant provisions in a consultancy agreement, external consultants will own the IP they create, and so the seller will need to evidence an effective assignment of all IPRs in the software to the business. Although copyright created in the course of employment will belong to an employer under English law, this is not necessarily the case in other jurisdictions, and it is good practice also to include assignment provisions in employment contracts. Local advice should be sought (e.g. in jurisdictions in which key software products have been developed) as laws differ across European jurisdictions – it is common for one law firm to coordinate the obtaining of this advice across the relevant jurisdictions.
If there is know-how which is important to the target business, it is important to ensure that this is adequately documented, has been protected by strict obligations of confidentiality and that, on receipt of such information, the buyer will be in a position to use it to operate the target business (otherwise transitional arrangements may need to be put in place to facilitate the effective transfer of know-how).