Discarded needles change position in the trash can as Jane cleans the Boss's desk.
When Jane is seen smoking a cigarette outside, it's snowing. Yet when Jane leaves the office for the evening, there is no snow or any other signs of moisture on the sidewalks.
In the morning, she gets into the car on the left side, but she gets out from the right side seat.
According to a White House invitation seen on screen, the month of December begins on a Wednesday. However, the laser-printed calendar page taped on the cabinet door behind Jane's desk only has 30 days. Since it's cold and snowing outside in New York City, the day being shown in the film has to be a day in November. However, the laser-printed calendar shows the 1st on a Wednesday. It is impossible for November and December to begin on the same day. Alternatively, if the day in the film is in December, they forgot to print a 31-day calendar.
Jane gets a car in the morning but not in the evening.
It has been noted as a "revealing mistake" that Jane has a driver in the morning but not in the evening. There are two plausible plot lines for this: 1. It is critical for Jane to be at work earlier than anyone to prepare the office for the day, so having her driven to the office is worth the expense, but not so important at the end of the work day; and 2. her boss was headed to L.A. that night and was using the driver for airport transport. Both plot lines continue the theme of Jane having value only when it is convenient or worthwhile to the overall office.