20 CFR § 226.72 - Benefits that do not cause a reduction.
The tier I is not reduced for the following types of benefits:
(a) A benefit paid under a law or plan that provided, on February 18, 1981, for reducing the benefit for entitlement to a disability insurance benefit under the Social Security Act.
(b) A Federal disability benefit based on service for other than a state or local government, if all or part of that service is covered under the Social Security Act.
(c) A disability benefit paid by the Federal government or a state or local government based on state or local employment, if all or substantially all of that employment is covered under the Social Security Act. “Substantially all” means 85 percent or more of the employment.
(d) A benefit paid by the Veteran's Administration.
(e) Private disability benefits.
(f) Amounts paid under the Federal Employers' Liability Act (FELA).
(g) Benefits based on need, such as welfare benefits or supplemental security income.