An IEP only applies to services provided by public schools. A 504 is backed by federal law and only applies to federally funded programs, including public schools.
Neither of these has any relevance if you are homeschooling or enrolled in a private school, such as an umbrella school. The GREAT news is that you also don’t need them when you teach your children at home because you can give them whatever adjustments in curriculum and accommodations that they need without the red tape!
PRS recommends that you keep a copy of all 504 or IEP records for reference if your child ever returns to public school.