Explanation here:

Un paso más en este método es la autoprestación. Esto es, cuando un centro auxiliar trabaja para sí mismo. Esto es normal, ya que, por ejemplo, las personas de un departamento de nóminas se hacen las nóminas para sí mismas, un departamento de Energía consume su energía o uno de Mantenimiento mantiene sus propios equipos
https://dokumen.pub/contabilidad-de-gestion-calculo-de-coste...

What Is In-House?
In-house refers to conducting an activity or operation within a company, instead of relying on outsourcing. This occurs when a firm uses its own employees and time to keep a division or business activity, such as financing or brokering, in-house.

An in-house operation is an activity performed within the same business, using the company’s assets and employees to perform the necessary outsourcing involves hiring outside assistance, often through another business, to perform those activities instead of using internal assets or employees.
https://www.investopedia.com/terms/i/in-house.asp

...note that integrated or bundled services offer ‘reduced costs, management of
risk, access to technical expertise, improved management information,
and value for money’ in comparison to in-house service provision
https://www.i-fm.net/documents/Perpetuity Security Report 9_...