is the amount of income required to file a tax return for a single person $10,400?
I made less than that. should I file anyway?
Yes, a single person under the age of 65 must file a tax return if your gross income was at least $10.400 (for 2017).
However, if income taxes were withheld, you may consider filing if you believe you are due a refund of those taxes. See this post for more help: If I don't need to file a return, should I go ahead and file one anyway?
Some reasons you might want to file are if you had taxes withheld and want them refunded; if you're eligible for the Earned Income Credit (you might get a refund even if you didn't pay taxes), if somebody else is claiming you as a dependent; or in some cases you'd need to file if you're getting health care from some version of Obamacare or if you owe social security taxes on income you got a 1099 for. There might be other reasons, IRS Publication 501 lays them out. You can read it online here.