0 to write the necessary information on an official document -- 填写（正式文件）
to fill in a form/questionnaire 填写表格／调查问卷
I had to fill in this really complicated form.
To find out more about our products, fill in the coupon and send it to us at the address given below.
Please fill in/out the application form with black ink.
Would you mind filling in a questionnaire about what you watch on television?
Charlie never fills in the record forms, which ruins the whole ordering system.
