The first point to consider is there are times you should file a tax return even if it not required. Here are the more common reasons:
1) If you had any federal or state tax withheld you may want to file a return in order to get a refund of the taxes withheld.
2) If you have earned income you may qualify for the Earned Income Tax Credit (EITC). The amount of the credit can be substantial.
3) If you have earned income and children you may qualify for the Additional Child Tax Credit (ACTC) which is a refundable tax credit. A married couple with two children under 17 and $20,000 in wages and no withholding can receive a federal refund of over $8,400 between the EITC and the ACTC even though they are not required to file.
4) If you paid for higher education you may qualify for the American Opportunity Credit.
Here are the general thresholds.
For Single Individuals: If your total taxable income is less than $12,200 or $13,850 (if over 65) filing is not required.
For Married Filing Joint Individuals: If your total taxable income is less than $24,400, $25,700 (if one spouse is over 65) or $27,000 (if both spouses are over 65) filing is not required.
For Head of Household Individuals: If your total taxable income is less than $18,350 or $20,000 (if over 65) filing is not required.
For Married Filing Joint Individuals: If you have taxable income you need to file a return.
For Qualifying Widow(er) with Dependent Children Individuals the same threshold as married filing joint apply.
It is a little more complicated for Individuals who are claimed on someone else’s return but in general the thresholds are you are not required to file if you have unearned income less than $1,100 or if you have earned income less than $12,200. If the total of your earned and unearned income is greater than $12,200 then you are required to file.
There are other situations where you may be required to file even if you are below the thresholds. The most common being if you had net earnings from self-employment of at least $400.