I am single head of the household and only collect SSI as income. Do I need to file to get the child tax credit?

[DoninGA]

If you do not have any earned income then you would not be eligible for the Child Tax Credit.  Social Security benefits received are not earned income.

SSI is Supplemental Security Income and is not from the Social Security Administration. It is designed to help aged, blind, and disabled people, who have little or no income; and. It provides cash to meet basic needs for food, clothing, and shelter. SSI is not reported on a tax return.

Social Security Retirement/Disability/Survivors benefits are reported on a form SSA-1099 and the benefits received are to be entered on a federal tax return. The benefits may be taxable depending on the amount of other income you have entered on your tax return.

However, if the Social Security benefits are the Only income to be reported on the tax return, then there is no reason or need to file a tax return.

[Opus 17]

Yes you should file this year, because of the economic stimulus and enhanced child tax credit.  

The American Rescue Plan Act includes an enhanced child tax credit of $3000, or $3600 for children under age 6 that is fully refundable even if you do not have income earned from working. This credit will be paid (supposedly) starting on July 1 by the IRS directly to taxpayers in monthly installments. (I say “supposedly“ because the law directs the IRS to make monthly advanced payments but the IRS may or may not actually be able to do that.)

If you want those monthly payment starting on July 1, 2021, you will need to file your tax return now claiming the dependent, so you are in the IRS system as qualifying for the enhanced credit. If you don’t file a tax return and the IRS does not know you have a qualifying dependent, you would be able to claim the credit on your 2021 tax return.

Also for 2020 tax returns, if you did not receive the $500 round one stimulus payment and the $500 round two stimulus payment for your dependent, the only way to get those payments is to file a 2020 tax return. Additionally, filing a 2020 tax return claiming the dependent will get you on the IRS notice to pay you the round three stimulus payment, which is $1400 per individual and $1400 per dependent.