IEPs and 504 Plans can both provide for accommodations, but they are guided by separate laws. The IEP is a plan for a child's special education experience at school, while a 504 Plan is a plan for how the school will remove barriers and provide support for a child with disabilities (Understood).
A 504 Plan satisfies Section 504 of the Rehabilitation Act of 1973, a federal civil rights law meant to stop discrimination against people with disabilities. A 504 Plan can serve students at both the K–12 and college levels, providing services and changes to the learning environment to enable a student to learn alongside their peers. A 504 Plan does not have to be a written document, but it typically includes the accommodations or supports the child will receive, who will supply them, and who is responsible for making sure the plan is implemented (Understood).
An IEP answers to the Individuals with Disabilities Education Act (IDEA), a federal special education law for children with disabilities. An IEP provides for specialized instruction for students in grades K–12 (Corsetto, 2020). The IEP must be a written document that sets specific learning goals for the child and describes the services the school will provide (Understood).
To obtain either plan, a child must have a disability as defined by the IDEA or Section 504, and that disability must have a negative impact on the child's ability to learn in a general education classroom. In fact, to qualify for an IEP, the child must require specialized education to make progress in school (Understood). If your child doesn't qualify for an IEP, a 504 plan could help provide the accommodations they need.
Please refer to Understood.org's comprehensive chart of the differences between IEPs and 504 Plans.
See also the Children's Hospital Wisconsin's IEP and Section 504 pages for details about the kinds of accommodations and expectations you'll see in each plan, and your legal rights: