Justify custom software through the decisive gap
A counterexample shows why unfamiliar labels and a missing mandatory step need different assessments.
Which difference obstructs the work?
An unfamiliar menu or different field label first calls for checking usability and configuration. A custom-software decision needs a concrete task that existing capabilities cannot adequately support. This makes it possible to explain which additional development is actually needed.
The following example is fictional. A service business evaluates an existing product for customers, jobs and reports. The labels do not match the language staff are used to. The business also requires a different authorised person to approve a report before the customer sees it.
Requirement | Candidate in the example | Next check |
|---|---|---|
Terms and operation fit the work | Menus and field names are unfamiliar; the basic workflow exists. | Try configuration and actual use; establish whether the difference causes relevant errors. |
Separate approval before customer access | This candidate’s intended facilities cannot support the required step. | Check other products, suitable extensions or targeted integration against the same requirement. |
Establish the size of the gap
In the first case, the existing product may suffice after suitable configuration. If the trial reveals real usage errors or an access barrier, that difference also matters. A different colour alone and an unworkable mandatory step have different consequences.
In the second case, the workflow remains unresolved. This justifies examining an extension or custom solution but does not establish that every existing product is unsuitable. If the decisive gap remains after comparing suitable alternatives, the development needed can be described concretely.
For that scope, also compare data transfer, maintenance, updating and later changes. GOV.UK’s purchasing guidance considers lifecycle and existing capabilities too. For your business, what matters is who can actually operate and develop the chosen solution. A custom build brings those tasks with it; a purchased product also needs reliable maintenance.
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