When not on leave, all thieves have a quota in Ankh-Morpork. This is based on guild level and sets both minimum and maximum amounts you must steal, and pay guild tax on, for every 12 hours that you play.
Minimum and Maximum
Your Minimum quota is your guild level divided by 4, in dollars ($0.25 per guild level).
Your Maximum quota is your guild level plus 100, in dollars.
Your guild fees are 30% of the amount you steal. Note that for some shoplifted items, the value reported to the guild may not be the same as that receipted on your quota.
Fees are paid to Artan, 2nd floor of the AM Thieves Guild classroom area.
If you fail to steal enough, or if you steal too much, the guild will fine you.
You can go on leave, or return from leave, by speaking to Kordane. New members of the guild always start out on leave.