Up to 85% of Social Security becomes taxable when all your other income plus 1/2 your social security, reaches:
Married Filing Jointly: $32,000
Single or head of household: $25,000
Married Filing Separately: 0
If you only get ssi or SS or SSDIit is not taxable and you do not have to file a return. And there is no benefit in claiming dependents or deductions. Unless you have federal income taxes withheld from the benefits or you get health care insurance through one of the state marketplace exchanges and receive a Form 1095-A then you need to file a tax return.
The previous reply from VolvoGirl is mostly correct for most people, but omits some details and variations - of which there are many.
I suggest using the IRS Interactive Tax Assistant, which walks you through a series of specific questions to determine whether or not your social security income is taxable, and if so, how much.