The Rules of Golf require that in stroke play every competitor has a marker to attest their score on each hole of their stipulated round. Both the player and their marker have an explicit responsibility for the correctness of the player’s score card. The Definition of Marker is;

A “marker” is one who is appointed by the Committee to record a competitor’s score in stroke play. He may be a fellow-competitor. He is not a referee.

Rule 6-6a deals with recording scores;

After each hole the marker should check the score with the competitor and record it. On completion of the round the marker must sign the score card and hand it to the competitor. If more than one marker records the scores, each must sign for he part for which he is responsible.

Note that a player may have more than one marker during their round. So, if the marker they start with cannot complete their round for any reason, such as sickness/injury or responding to an emergency, they must sign the player’s score card for the holes that they were present to witness and hand it over to another person to complete the remaining holes. If a player is not accompanied by a marker for any hole of their round they do not have an acceptable score for the competition (Decision 6-6a/2). It follows that an unaccompanied pair in a four-ball or foursome cannot return a valid score card, as they may not mark their own score card.

Rule 6-6b deals with the signing and returning of a score card;

After completion of the round, the competitor should check his score for each hole and settle any doubtful points with the Committee. He must ensure that the marker or markers have signed the score card, sign the score card himself and return it to the Committee as soon as possible.

Some marker’s (and players!) sign the score card as soon as they receive it, so that they cannot forget to do it at the end of the round. This is obviously not acceptable, as the Rule 6-6b states, “After completion of the round.….