I need to amend my 2021 tax return in order to add a dependent and therefore get the respective credit(s) and/or respective deductions reflected in my amended tax return?

[sus-chong]

My boyfriend (now deceased) lived with me all year in 2021. He did not have a job. I had a job and took care of both of us financially in every single way. Which credits and/or deductions apply to this scenario?

[ThomasM125]

I think you mean you want to treat your companion as your dependent. If so, if the individual was over the age of 16, you may be entitled to a credit, or reduction of your tax, of $500 for the dependent, for the "other dependent" credit. The individual must qualify as your dependent, meaning you furnish over half of their support and they earn less than $4,700 during the year. Also, they can't be claimed as a dependent by anyone else, must have a valid social security number, are a US citizen or resident alien or US national. They can't file a joint return with anyone else. Also they must lived with you for the entire year, or until they became deceased in this case. 

Also, you may be able to qualify for head of household filing status if you support an other dependent. This may reduce your income tax rate and therefore the tax you owe. You will see an option to choose that status when you enter your personal information in TurboTax.