Social Security Guarantee Act of 2023 This bill requires the Department of the Treasury to issue certificates to Social Security beneficiaries that guarantee them the full monthly benefit amount to which they are entitled and at least an annual cost-of-living increase to their benefits. It also provides additional mandatory funding for those benefits. Currently, Social Security beneficiaries are entitled to their benefits, but benefits are primarily funded through a payroll tax (including assets derived from the tax held in reserve). Actuarial projections reported by the Social Security Board of Trustees indicate that in 2035 there will be insufficient tax revenue and reserved assets to cover the full amount of benefit payments.