College student using laptop in library © HBSS, Corbis

The only thing louder than the cheers from college acceptance letters are the hisses from students who didn't get enough financial aid. Don't worry -- the game's not over yet.

Even if your college has already sent out award letters, there are special circumstances where it will sweeten a financial aid package at the last minute. Although it may take some extra paperwork and a few trips to your school's financial aid office, it might mean the difference between needing to take out a private student loan or not going to your choice college at all.

Here are some of the times the financial aid office can adjust your package for the better.

1. Your circumstances have changed

Your financial aid package is based on your family's assets and earnings from the previous year. Any major fiscal changes you've had since last year may warrant an adjustment in aid, says Trina Wilson, interim director of financial aid for the University of California, Davis.

"We will look at things like a layoff or unemployment, disability that may have changed the family's income," Wilson says. "There can be a retirement. There can be an unfortunate death in the family, divorce, some child support changes."

If your family has had a significant change in circumstance that's not reflected in your financial aid paperwork, be ready to prove it. In order to get a last-minute boost in college cash, aid offices require documentation, which may include things such as past pay stubs, tax information or divorce records.

2. There's been a mistake

The Free Application for Federal Student Aid, or FAFSA, the application the government uses to determine your federal aid package, can be filed as early as Jan. 1, but it requires tax information that may not be officially available until tax season in April. To get the FAFSA in early and take advantage of awards that are doled out on a first-come, first-serve basis, many families estimate their tax information and then file a correction later. If your estimate was off or you made a different FAFSA mistake, you could be due for a change in aid, says Vonda Garcia, financial aid director for California State University San Marcos.

"(Families) would initiate the change by going to FAFSA.gov. They go online and just update their information," Garcia says. "Sometimes a $100 difference could bump them into a different eligibility limit. If there are any corrections to be made, we always encourage families to make them."

After filing a FAFSA change, Garcia says that it generally takes anywhere from two to four weeks for her financial aid office to update its records and review an aid package in light of the new information.

3. Your family's growing

Changes in the size of a family can also impact how much aid is offered. If there's a new pregnancy, a sibling who's also unexpectedly going to college or a relative who's moved into the household and is currently being financially supported, those circumstances could warrant a financial aid review, Garcia adds.

If you have a new family member or any valid reason for asking for an aid review, Wilson recommends contacting your financial aid office immediately and organizing the requested documentation as quickly as possible.

"The earlier (students) get that in, the sooner we can let them know something about their eligibility," she says.

4. Your enrollment changes

Since your financial aid package is partially based on your college costs, upping those costs by moving from part-time to full-time enrollment may warrant a review of your aid package, says Tim Opgenorth, executive director of financial aid for the University of Illinois, Chicago. So can adding extra classes or attending summer school, if it ups tuition costs.

"Some schools charge different tuitions for different majors, so if a student changes majors, that calls for (a financial aid change), too," he says.

Opgenorth adds that if your financial aid package does get adjusted, that doesn't necessarily mean you'll be given more gift aid.

"Usually, with cost of attendance increases like that, in most cases it doesn't affect any sort of grants or scholarships the student receives," he says. "In most cases, it would just affect loan eligibility. That's also something (students should be) aware of."

5. You're independent

Financial aid packages for dependent undergrads are primarily based on their parents' income and assets from the year before. Financial aid packages for independent students don't include parental financial information and can often be significantly higher. The federal government maintains strict eligibility requirements for independent students: You basically have to be age 24 or over, a veteran or currently serving in the military, married, a graduate student, in foster care, a legally emancipated minor or a parent to qualify, according to the Department of Education.

There are situations where students don't meet independent status requirements, but also aren't receiving financial help from their parents. In those rare circumstances, students can apply for a "dependency override" through their financial aid office, which may result in an increase in aid.

According to FinAid.org, "approximately 2 percent of undergraduate students become independent through such dependency overrides." Documentation requirements for dependency overrides vary significantly depending on the circumstance, but Wilson says that schools often require a statement explaining the situation from the student, as well as supporting evidence from third-party sources such as school counselors or attorneys.

6. Your costs are above average

"The cost of attendance that we use to determine the student's (aid) eligibility, that's based on averages," says Garcia. "We're obviously not looking at each student's individual costs unless they bring it forward and we see that their costs are more than the average, but it's very subjective."

If you have a college expense that's not factored into a school's cost of attendance or a home expense that's not considered in the financial aid methodology, that could warrant an aid review, says Garcia. Colleges typically include tuition, room, board, transportation, books and fee estimates in their cost of attendance, but expenses such as high medical or dental bills won't be included.

Another common price jack is increased costs associated with studying abroad, says Opgenorth.

"We have a standard amount for transportation (factored into UIC's cost of attendance) that's basically meant for students on campus," he says. "If now they're going to go to Europe for a semester, the cost of the plane ticket and stuff like that is obviously more expensive. As long as they can provide us with documentation to show us, we definitely have the latitude to increase the cost of attendance."

Click here to become a fan of MSN Money on Facebook

More from Bankrate