Life insurance proceeds are not taxable to you, except for any interest income paid with the proceeds. Please see the link below:
https://www.irs.gov/help-resources/tools-faqs/faqs-for-individuals/frequently-asked-tax-questions-an...
You asked about the death benefit paid by Social Security.
If you are referring to the $255 lump sum death payment, then no it is not taxable. Any other Social Security benefits taxes are calculated according to the Social Security Benefits Worksheet, which you can find at the link below:
https://apps.irs.gov/app/vita/content/globalmedia/social_security_benefits_worksheet_1040i.pdf
