A common error is showing up on the 1987 Maryland income tax returns of senior citizens, the group most affected by revisions in the state's tax code, according to Comptroller Louis L. Goldstein.

The legislature eliminated the personal exemption for senior citizens last year, and substituted an $800 standard deduction for taxpayers and their spouses who are 65 or older.

To receive the deduction, senior citizens must check the box at the upper right corner of the return indicating they are 65 or older, or blind. Many are not doing so. Unless the box is checked, the computers will not allow those taxpayers the deduction, Goldstein said yesterday.

Some senior citizens also are making the mistake of still trying to claim the extra personal exemption, which was eliminated. Those who do make such claims will eventually be billed for the amount of additional tax due, plus penalty and interest, Goldstein said.

The only senior citizens who remain eligible for the extra personal exemption are dependents, other than the taxpayer or spouse, who are 65 or older.

An example would be a parent living with a child, where the child provides more than half of the parent's support.

Other reminders for senior citizens:

Taxpayers 65 or older or totally disabled may be eligible for Maryland's pension exclusion of up to $9,100, which appears on the back of the state's long form.

Taxpayers who had to report some of their Social Security or railroad retirement income on their federal tax returns should remember that Maryland does not tax that income. A special brochure is available describing how to claim this benefit.