It is frustrating when you complete a job and then you are checking your account every day expecting to see your earnings and nothing happens. In my experience, most MTurk requesters pay up within a couple of days. Some pay quicker than that, within a matter of hours sometimes. The annoying thing is where is takes over a week before you receive your MTurk payment. You can email the MTurk requester in this situation, but be aware that Amazon allows them up to 30 days to either pay or reject your work. That is way too, long in my opinion, and Microworkers have got a better idea by giving MTurk employers a one week cut off period to resolve outstanding jobs.
Non-payment by MTurk requester because of hits rejected
Occasionally you can get hits rejected by an MTurk requester and it seems unfair. As well as losing the money you felt you earned, getting hits rejected can also damage your hit rejection rate and effect which hits you are able to do in future. So even if the amounts of money involved are small, it can still be annoying and upsetting.
If there were technical problems at the time of doing the hit, then you should report the hit as broken using the link in the bottom right. If you believe that the requester is breaching the Amazon Mechanical Turk policies, then you should click the “Violates the Amazon Mechanical Turk policies” link which is also at the bottom right.
Sometimes you have no idea why you have had your hits rejected. In this case it is best to contact the MTurk requester. I would advise that the tone you adopt with them is polite but firm. You should explain that you followed all the instructions and ask why your work was rejected. In many cases the matter can be resolved this way and you will get your money (or they will explain to you your mistake). Sometimes the MTurk requester will use stalling tactics and you have to write more than once before they pay up. Note though, that an MTurk requester cannot themselves reverse a rejection decision without the help of Amazon.
If you still have no joy, then your options for complaint as an MTurk worker are very limited (one gripe of turkers is that MTurk requesters can ban certain MTurk workers, but not the other way around). Though you can, of course, warn other MTurk workers about the bad requester and discuss your experiences either on Turkopticon, or on one of the MTurk forums.