If your child receives Supplemental Security Income (SSI) benefits and is going to turn 18, you should talk with your special needs planner about some important changes that could significantly impact your child's SSI benefit.

About one in three children who receive SSI lose their benefit when they turn 18 years old.  This often happens because the Social Security Administration (SSA) uses a different test to determine disability once a beneficiary turns 18.  Prior to age 18, a beneficiary is considered disabled if he has a mental or physical impairment expected to last at least 12 months that results in “marked and severe functional limitations.”  However, once the beneficiary turns 18, his impairment must “result in the inability to do any substantial gainful activity.”  The adult disability standard is a higher one and many beneficiaries are dropped from the rolls because they fail to meet it.

Fortunately, the SSI financial requirements often become easier once a child turns 18, because at that point the SSA looks at the beneficiary's own income and resources instead of using the beneficiary's parents' financial record.  Since many SSI beneficiaries who received benefits as children don't have any other sources of income and don't own any large assets, they likely won't have any problem qualifying financially on their own.  In some cases, a person who qualifies as disabled but can't meet SSI's financial requirements due to her parents' income or resources may immediately qualify for benefits once she turns 18.

It's also possible that an SSI beneficiary won't lose her benefits when she turns 18 and fails to meet the new disability or financial requirements.  A beneficiary can continue to qualify for SSI under the pre-18 rules if she participates in an approved vocational rehabilitation program or special education program that began before the beneficiary turned 18.  In other cases, SSI beneficiaries who regularly attend school are allowed to exclude $1,780 of income a month, up to $7,180 a year, from their countable income for SSI purposes.

Because these rules are complicated, it's essential for you to meet with your special needs planner well in advance of your child's 18th birthday in order to learn how his or her birthday is going to affect SSI benefits.

The SSA has a brief overview of the age 18 changes here.