QTSP
A QTSP, a Qualified Trust Service Provider, is a trust service provider that a EU member state supervisory body has granted qualified status and listed on that country’s Trusted List, making it the party allowed to issue qualified certificates, a QES or a QEAA under eIDAS.
Any organisation can offer a trust service, but only one supervised and audited against the eIDAS qualified requirements earns a place on a national Trusted List, and only that listing lets a relying party trust its output without checking further. A QTSP is what makes a QES a qualified electronic signature rather than an advanced one, and what makes a QEAA carry the legal presumption of accuracy that a regular EAA lacks: both depend on the issuing party being a QTSP, not merely a trust service provider. Losing or never obtaining qualified status does not stop an organisation from operating; it just means its output no longer benefits from the legal weight eIDAS reserves for QTSPs.