Medical insurance claims, income tax forms, college financial aid applications and hospital bills are the toughest documents to handle these days, a survey reported this week.

And the easiest? Mail-order forms.The survey of 625 adults nationwide by the Siegel & Gale Perplexity Poll asked them to rank common forms and documents according to their difficulty, reader satisfaction and attitude toward those required to fill them out.

"While Americans find most documents and forms easy to use, they have a terrible time understanding and completing materials that seriously affect them financially," commented Alan Siegel head of the New York-based communications firm that has spearhead the plain English movement since the 1970s.

On a scale of 0-100, college financial aid applications, federal and state income tax forms and medical and dental insurance forms were rated "unacceptable at 0-49, the survey said.

Hospital bills and mortgage applications had a "problem" rating of 50-69.

Car rental agreements, doctor bills, frequent flyer statements, insurance premium notices, loans and credit applications and telephone bills got an "acceptable" 70-79.

Bank credit card statements, credit card applications, utility bills, monthly bank statements and oil company credit card bills won a "good" 80 to 89.

Mail-order applications were ranked "superior" at 90 to 100.

In praising the plain English of mail-order forms, Siegel said they are "the lifeblood of businesses that survive on their ability to communicate with customers as clearly and easily as possible."