This grammar is used only in conversation. It is used when asking a question in order to confirm/affirm something.
*Because it an expression for confirmation, it is alright to use past tense when referring to something in the present or future. EX: 来月の三日は月曜日でしたっけ。(=月曜日だったっけ) "The 3rd of next month was Monday, right?"
*If you wish to use more formal Japanese, you can use 「ましたっけ」 or 「でしたっけ」, but you CANNOT use 「ますっけ」 or 「ですっけ」.
rubyhatchet
っけ is used as a question marker in informal Speech (and even then is often just shortened to け。)
っけ itself is generally used when asking about something you should really already know but have forgotten, or when you are affirming something that you're maybe 50% sure about.
反戦
I read in a Grammar Textbook that it means almost the same as -かなあ、or −かしら
your name
yes, so you can also say 誰だったかなぁ。誰だったかしら。-かしら is used mainly by female.
Miki
っけ may _only_ follow the あ-row of kana. Thus, だっけ and ましたっけ are correct, but してっけ or 食べるっけ, etc., are incorrect.
KyleGoetz
け (usually っけ) is used when asking about something you _should already know_ (e.g. because you've been told but since forgotten/become unsure).
Amatuka
ques.「ano resutoran ni soubetsukai shinai」 「あそこ 50人 入れる ほど 広かったっけ」 Please explain this.the second sentence is a question or giving explanation why the party cant be held there?
jayati
I often hear nan deshita-kke? ah, you know, whatchermecallit