to file an appearance (юр.) gen.

[zozobra]

... and the Respondent having been found in default for his failure to file his appearance or otherwise plead in this cause. (из судебного решения)

[AsIs]

а че тут? ну не явился в суд или ваще на все забил...

[AsIs]

(мне тоже лень формулировать)

[zozobra]

типа какую-то форму не подал, я подумал, может есть какой-то конвенциональный русский вариант

[алешаBG]

notice of appearance n.
1. A written document filed with the court (or in some cases, a verbal representation made in court) to notify it and the other parties that a party wishes to appear in or receive notice of the proceedings.
2. An attorney’s written or verbal notice to the court that he or she represents one of the parties.