Do you know what information is needed for the parents' section of the FAFSA form?
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Do you mean questions that ask for each parent?
yes
Just the basic information about your parent's identity, like their name, date of birth, and social security number; their living situation, marital status, state of residence, household size, and financial circumstances.
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How should I respond if they are separated?
 That would depend on if your parents live together or not. If your parents are married but are considered legally separated by a state, or if they legally married but have chosen to live separate lives then they are considered separate, as if they weren't married.
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What if my parents don't want to provide the required information for the FAFSA form, can I submit it without that info?
You could, but take into consideration that you would not receive an EFC and some state-school-based aid programs look at the EFC to determine your eligibility for their funds, if you don't have an EFC then you won't be eligible for those aid programs.
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And what if my parents live in one of the Freely Associated States?
Ask them to enter the Amount of Wages Earned from their Freely Associated States tax form in the field where the FAFSA form asks for adjusted gross income.
Another doubt I have is, what if my parents do not have a social security number?
Then just enter all zeroes on the field the FAFSA form asks for that information.
