ID pointers: Easily mistaken for Svensson’s Copper Underwing A.berbera.svenssoni. There is great conjecture on the correct methods of identification.
One of the most consistent features seems to be careful examination of the under hindwing. The underside of the hindwing’s discal area is a pale straw yellow and this contrasts with both the orange-copper terminal area and the blackish curved streak along the leading edge. Other features that can aid identification are:-

The cross-line just before the middle of the forewing has four projections along it which are all typically the same length.

The Labial Palps feature has been completely rejected as a means of identification. This is for interest only. The upward point labial palps at the front of the head are pale but can be unreliable if worn.

The upper-parts are brighter than svenssoni and more sharply defined. There is also a contrasting broken post median line but a duller and darker brown cross-band towards the trailing edge.

The Copper marking on the under hindwing is minimal along the trailing edge and the black and white colouring of the abdomen sides seems to be more intense.

If ID cannot be determined – then examination of the genitalia is required, as they show clear differences or record as aggregated (agg).