I work sales in a office,if I work over 40 hours in a week is my company required by law to pay me over time?

I work in Chicago Illinois

It also depends on whether you're considered an employee or an independent contractor.

Here is information about Illinois overtime laws:
http://www.state.il.us/agency/idol/laws/...

Guarantees a minimum wage of $7.50 per hour for workers 18 years of age and older; workers under 18 may be paid $.50 per hour less than the adult minimum wage. Credit for tips may not exceed 40% of the applicable minimum wage. Employers may apply for licenses to pay sub-minimum rates to learners and certain workers with physical and mental limitations. Overtime must be paid after 40 hour of work per week at time and one-half the regular rate.

You may want to open the PDFs and/or links:
http://www.state.il.us/agency/idol/forms...

I would think so.

That depends on the state or province you live in.

Some places say that overtime starts when you have worked 44 hours, and some places will not pay overtime until you have worked 48 hours. Check out the employment law for your state or province and read what it says.

Somewhere in your office there HAS to be posted notices.
They start with large pring "IT IS THE LAW" "Est Is La LEY"
There are other notices posted by law in the same area (try the lunch/break room). It will tell you your state's laws (NOT regulations) about overtime. If you can't find them ask a supervisor to show them to you. (by LAW, they have to do so)
If they are not posted ya better find out why. (I'd look for another job, too)

Unless your position is exempt from federal wage and hour laws, which it probably isn't, then yes your employer is required to pay you time and a half for hours over 40 per week.

Pretty much every state has a regular work week of forty hours, and anything over that must be compensated accordingly. Talk to HR.

No. Outside sales people are exempt.