If someone filed last year jointly with two kids 8 and 10 (for example), and this year is filing Separate, don't forget that this person will get on line 28, $4,500 as child tax credit and on line 30, it will get $1,400 as stimulus.
A lot of people don't bring the stimulus letter and when you ask them about the stimulus, they say "I received all the stimulus" and it is easy for the preparer to forget to click on line 30.