The new generation of real-time mission-critical applications requires high resilience and low-latency coordinated actions, surpassing the specifications outlined for 5G URLLC services. Examples include high-precision robot control and autonomous vehicles that cannot tolerate millisecond latency, and factory automation over wirelesslinks that demand sub-millisecond end-to-end latency. To support the next generation of URLLC use cases, referred to as eXtreme URLLC (xURLLC), 6G systems will need to make faster and more reliable decisions at the network edge. One essential requirement in terms of connectivity is determinism. Currently, the solution toincorporate determinism at the IP layer is defined by IETF DetNet specifications. In a DetNet domain, a DetNet stack is employed, consisting of two sub-layers: the Service sub-layer and the Forwarding sub-layer. This stack is documented in RFC 8655. What remains open is the definition of header fields in the application layer toincorporate determinism into the network. This paper presents a proposal for a DetNet header for the application layer.