Appointing party term introduced in BS EN ISO 19650 it is meant to replace PAS 1192 term ‘Employer’

ISO 19650 term depends on where in the hierarchy the employer is located.
The BS EN ISO 19650‑2 appointing party (A) is the equivalent of the PAS 1192‑2:2013 top‑level employer

Who is an Appointing party?

1. A Client who appoints Tier 1 Main Contractor
2. A party who is managing information on behalf of the client.^[1]

Technically speaking an Appointing party would be also a Tier 1 Main Contractor if he employs other sub-contractors, but is such a situation ‘appointor’ would be a more suitable description. In the context of the ISO 19650 framework, the Tier 1 Main Contractor who employs other subcontractors should only be regarded as Appointing party if such Tier 1 Main Contractor is managing information on behalf of the client.^[1]

Typically the Tier 1 Main Contractor will have a leading function named the Lead appointed party when appointed by the Client

Where an ISO 55001 asset management system is in place, “appointing party” is synonymous with the term “organization” in ISO 55001.

BS EN ISO 19650‑3:2020, 5.1.4 Note 2

1 Boutle, A., Dodd, P., Dearlowe, J., Hooper, E., Ford, J., Rossiter, D., Tennyson, R., Thompson, N., Winfield, M., Zahiroddiny, S., 2021a. Guidance Part 2 Parties, teams and processes for the delivery phase of assets, 6th ed, UK BIM Framework. UK BIM Alliance.