What are the FAFSA and CSS Profile and who has to file them?
The FAFSA is the federal aid form and nearly every family should file it, including families who assume they will not qualify. The CSS Profile is a separate College Board form that some mostly private colleges require in addition, and it asks more detailed questions about assets, businesses and non-custodial parents.
The FAFSA
It determines eligibility for federal grants, work study and federal loans, and many states and colleges use it for their own aid too. File it even if you expect to receive nothing: some merit awards and institutional aid require it, and the cost of filing is an hour. Confirm the current opening date and requirements at studentaid.gov, because the schedule has shifted in recent cycles.
The CSS Profile
Required by a subset of colleges, mostly private and mostly those with large institutional aid budgets. It looks deeper than the FAFSA: home equity, small business value, and in many cases the finances of a non-custodial parent. Families with divorced parents or self-employment income frequently find this form determines their result far more than the FAFSA does. There is a fee, with waivers available.
The deadline that actually matters
Not the federal one. Each college sets its own priority deadline for institutional aid, and those are often earlier. Miss a college priority deadline and you can lose money while remaining perfectly eligible on paper. Build the list of per-school aid deadlines at the same time you build the college list.
Practical notes
File with the tax year the form asks for rather than the current one. If your circumstances have changed since that year, say so directly to the financial aid office; there is a formal process for it. And be wary of any service charging to file the FAFSA, since the first F stands for free.