What happens if I overstay my tourist visa?

Thanks, my wife told me that, too, after I had written this post!

It is best to pay the fine in town rather than at the border, cause they could put the screws on you there.

:-)

If you find yourself in a situation where you must stay in Peru longer than the time allotted on your visa, you will be charged a $1 US per day fine when you leave the country.  So, if you overstay your visa by a week, you'll have to pay a fine of $7US. At the airport, you'll pay the fine to the immigrations officer as you leave, after you've paid the regular airport tax. If you are leaving Peru by land at one of the major border crossings, the process is similar – you pay the fee to the Immigrations officer as you leave. They should give you a stamp and a receipt that you can keep in your passport.  It is not recommended that you try to leave through one of the smaller border exits if you have overstayed. Some expats have overstayed by very long lengths of time (I've heard of up to 6 months) and simply paid the fee when they left.  However, remember that this IS Peru – while it's unlikely that you'll ever have problems, you CAN get in trouble for being in the country illegally.  It is always recommended that you try to maintain a legal tourist visa. 
see http://www.expatperu.com/overstaying-pe … -visa.html

How about renewing a visa that has expired?  My daughter is in Lima for one year at school.  She failed to convert her tourist visa to a student visa and it is now expired. While her school would like to help, they have told her that the only way to get a new visa is to leave and enter again.  How long does she have to be out?  She has an airline ticket to leave Peru in August, but this seems to exceed the time for which a tourist visa is valid so will this be a problem if she tries to come back in?  I am of the opinion that it is better to pay a couple of hundred $ to get her a valid visa than to have her trying to pay a fine for overstaying by 6 months.