For the LW: a witness, the approval of your Komandeur and the final approval of the Oberkommando der Luftwaffe.The last point in effect made all claims primo marts 1945 onwards non-official, according to  Eric Mombeek "Reichverteidigung.Die Geschichte des Jagdgeschwaders 1 "Oseau"".
Col. Raymond F. Toliver, USAF (Ret.) & Trevor J. Constable have some interesting views in their "Fighter Aces of the Luftwaffe":
" On the Eastern Front, the Luftwaffe produced the highest scoring aces of all
 time.  They are Erich Hartmann, with 352 victories, Gerhard Barkhorn with 301,
 and Gunther Rall with 275 victories.  Other top-scoring Germans in Russia were
 Otto Kittel with 267 victories, Walter Nowotny with 258 downings, and Willi
 Batz with 237.  These men are but the top scorers.  There were numerous lower-
 scoring but eminent pilots such as "Macky" Steinhoff with 176 victories, Tony
 Hafner with 209, md Hermann Graf - one of Germany's popular wartime he-
 roes - with 212 aerial victories, and Wilter Scluck, 206 victory ace from the
 frozen north of Finland.
     These scores are enormous by the standards of the contemporary USAAF,
 RAF and Soviet Air Force.  There was a consequent reluctance, for many de-
 cades, to accept these huge German scores as valid.  This passed in due time, as
 non-German historians finally examined and analyzed German records and pro-
 cedures.
     The authors have spent sufficient time interviewing German aces, examin-
 ing records, logbooks, wing histories and other official documents over a forty
  year period, to have no doubt as to the thoroughness of the Luftwaffe scoring 
 system.The German system was rigid.British and American scoring procedures were
 far less demanding, and allowed such mythical accredations as one half, one
 third  or three quarters of a victory - the so called shared victory.
  The German penchant for precision could not abide such ideas as a pilot
  down half an aircraft.  This fiction was eliminated by a simple set of rules.
  Were more than one pilot was involved in a downing, the pilots had to decide
  between themselves who best deserved the credit.  In the event of an im-
  passe, the downing was credited to the pilots' unit, with no individual pilot credit
  awarded.
  A typical case occurred on 22 March 1943, when First lieutenant Heinz-
  Schnaufer, later to become the top scoring night fighter ace of the war,
  a victory over an RAF Lancaster.  Captain Wilhelm Herget, later Major Herget and          credited with seventy-two victories by war's end, claimed the same aircraft.
  In the dark, both of them had engaged the same bomber.  General Kammhuber
  of the night fighters ordered the two aces to draw lots to settle the matter.
  Herget won.
  Under the USAAF system, by contrast, it was possible for a pilot to become an
  ace without ever scoring a clear victory of his own.  He could reach five victo-
  ries on shared credits.A mathematical substraction could become a substitute for genuine   achievements.The USAF contuined the quistionable tradition though the Korean War and into   the Vietnam conflict.In 1966, the USAF further  adulterated its already suspect victory   credits system by announcing that victories scored by USAF aircraft with a crew of two - a  pilot in the front seat and a "guy in back" - would be accredited by giving both pilots a   victory credit.  Thus, five enemy aircraft downed, creates two American aces!
        The Luftwaffe system was clearly more rational and realistic.  "One pilot -
  one victory" was the straight forward scoring rule.  Without a witness, a Luftwaffe
  pilot had no chance of victory confirmation.  Such a claim, even if filed. would
  not pass beyond his Gruppenkommandeur.
        The final destruction or explosion of an enemy aircraft in the air, or the bail-
  out of the pilot, had to be observed either on gun-camera film, or by at least one
  other human witness.  This witness could be the German pilot's wingman, squad-
  ron mate, or a ground observer of the encounter.  There was no possibility, as
  with some RAF and USAAF pilots, of having a victory credited because the claim-
  ing officer was a gendeman of his word.  The Luftwaffe rule was simply "no wit-
  ness - no victory credit."
        This rule applied universally in the Luftwaffe, no matter what the pilot's
  rank or ace status.  The authors have a photostatic copy of one of Galland's own
  wartime combat reports of a downing.  The report concludes with, "I resign the
  confirmation of this victory for lack of a witness."
        The Luftwaffe system was impartial, inflexible and far less error-prone than
  British or American procedures.  German fighter pilots sometimes had to wait
  more than a year for victory confirmation to reach them from the Luftwaffe High
  Command.  There are some examples in this book.
        The Germans differed radically from the Allies with the Luftwaffe's compli-
  cated "points' system, instituted to bring a modicum of uniformity into the be-
  stowal of higher decorations.  The Allies had no such points system.
        In effect only on the Western Front, points were awarded for decorations as
  follows:
        Single-engined plane destroyed 1 point
        Twin-engined plane destroyed 2 points
        Three-engined plane destroyed 3 points
        Four-engined plane destroyed 3 points
        Twin-engined plane damaged 1 point
        Three or four-engined plane damaged 2 points
        Final destruction, damaged twin-engined plane 1/2 point
        Final destruction, damaged four-engined plane 1 point
        The Germans set great store by the ability of a fighter pilot to separate indi-
  vidual Allied bombers from the box formations in which they flew.  Thus, a
  Luftwaffe pilot could not win points for damaging an Allied bomber unless he
  separated it from the box - the separation being known as Herauschuss.
        This points system for decorations, has been confused in past years with
  normal victory confirmation procedures.  Much inaccurate material has been
  written about the German scores because of this confusion.  A practical example
  of the two systems, as they worked during the war, mill provide clarification.
        Suppose it is early 1943, at which time forty points were needed to qualify a
  fighter pilot for the Knight's Cross of the Iron Cross.  Our hypothetical pilot, Captain   Flugmann, has already shot down and confirmed twenty-two single-
  engined fighters (twenty-two points), five twin-engined bombers (ten points), and
  two four engined bombers (six points).  Flugmann is an ace with twenty-nine victo-
  ries, but he has only thirty-eight points - not enough for his knight's Cross.
       Flugmann takes off next day and damages a B-17, separating it from its box
  formation.  He also brings about the final destruction of a second B-17 damaged
  previously by another German pilot.  Flugmann now has forty-one points, enough
  for his knight's Cross, but he is credited with thirty victories after reconciling the
  air battle with other pilots and getting victory credit for one of the bombers.
       This point-decoration system was used only on the Western Front, because
  the Germans believed it was easier to shoot down Russian fighters and bombers
  than to down Western-flown aircraft.  The Germans considered the mighty Al-
  lied bomber streams, with their lethal volumes of protective fire and hordes of
  escort fighters, to be a far tougher proposition than Soviet air power.
       Although the point-decoration system for the Eastern Front was not in ef-
  fect, victory-confirmation procedures and requirements were the same on both
  fronts.  Late in the war, there were pilots on the Eastern Front with over 100
  victories, who had still to receive the Knight's Cross awarded for forty points won
  in the West."
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