When it comes to writing, rules can be a wonderful thing. They help ensure consistency, and they relieve writers from having to make endless decisions about mundane questions like which punctuation mark to use. Sometimes, though, usage rules can get in the way of clear communication. In creative writing or informal communication like email, writers have the freedom to reject those rules if they don’t find them useful.
The rules say to use a question mark in the following situations:
- At the end of a direct question: Whose meatball is that?
- To express doubt or uncertainty: Leona was born in 1960[?], which would mean her current age is 49.
- To express confusion or disbelief: You call that a sandwich?
According to the Chicago Manual of Style, a “courtesy question” does not require a question mark. For example, “Will you please remove your shoes before entering the sanctuary” is a statement, not a question.
In Modern American Usage, Bryan Garner puts it this way: “A question mark follows every question that expects an answer.”
Sometimes, though, I expect an answer even if I don’t phrase the sentence as a question. Consider the following: “I wonder if I have time to stop at the post office before lunch?” This is the reverse of a courtesy question: it’s a question phrased as a statement. What I mean is, “I want to stop at the post office before lunch. Do you mind?” But this phrasing makes it awkward for someone to say, “I’ve got a 1:00 meeting. I was hoping everyone could be at the restaurant by noon.” So I cloak my desire in an absent sort of wondering to make it easier for someone to tell me no.
Technically, an indirect question should not end with a question mark. But in email, I often find it useful to end a statement with a question mark if I want the reader to respond. In dialogue, this practice can be useful as well, to convey that a character lacks conviction or habitually defers to others.
Another case where I prefer to break the rule is with tag questions. According to Fowler’s Modern English Usage, “a tag question (e.g. He’s much taller now, isn’t he?) must be followed by a question mark.” In dialogue, however, I find the question mark misleading if the voice inflection doesn’t indicate a question. If I don’t want the reader to hear the pitch of the character’s voice rise, I don’t use the question mark—for example, “You ate too much Halloween candy, didn’t you,” Margie said to her son. Again, this is a statement, not a question.
Undoubtedly, some sticklers will find this usage grating. It might lead some readers to think I don’t know the rules. But that’s a chance I’m willing to take for the sake of clarity.
Write with Personality 
Statements as questions? Very well said.