Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

Received an unexpected cashiers check for over $2K from another state - is this some scam?
It is likely a scam.  In fact the whole mystery shopping "job" may be a scam.  There is a Snopes page about cashier's check scams, as well as a US government page which specifically mentions mystery shopping as a scam angle. As for how the scam works, from the occ.gov site I just linked: However, cashier’s checks lately have become an attractive vehicle for fraud when used for payments to consumers. Although, the amount of a cashier’s check quickly becomes "available" for withdrawal by the consumer after the consumer deposits the check, these funds do not belong to the consumer if the check proves to be fraudulent. It may take weeks to discover that a cashier’s check is fraudulent. In the meantime, the consumer may have irrevocably wired the funds to a scam artist or otherwise used the funds—only to find out later, when the fraud is detected—that the consumer owes the bank the full amount of the cashier’s check that had been deposited. It is somewhat unusual in that, from what you say, there has been no attempt thus far to get money back.  However, your sister-in-law may have received that info separately, or received it as part of her mystery shopping job but didn't mention it to you with regard to this check.  Typically the scam involves telling the recipient to transfer money to a third party (e.g., by buying goods as a mystery shopper, or via wire transfer to "reimburse" someone associated with a sham operation).  By the time the cashier's check is revealed as fraudulent, the victim has already transferred away his/her own real money. It's probably worth taking the check to your or her bank and asking them about it.  They may have more info.  Also, banks usually want to know about scams like this because, in the long run, they accumulate data on them and share that with law enforcement and can eventually catch some of the scammers. Edit: Just to help anyone who may be reading this later.  The letter you added confirms it is absolutely a scam.  My boss was once contacted via a scam operation very similar to this.  The huge red flag (in addition to others already mentioned) is that you are being "given" a check for over $2000, of which only $25 is purportedly for actual mystery shopping and $285 is payment for you, the mystery shopper.  The whole rest of the $2000+ amount is for you to wire to "another Mystery/Secret Shopper in order for them to complete their assignment".  They are giving you $2000 to give to someone else who is supposedly another one of their own employees/contractors.  Ask yourself what sane business would conduct their operations in this way.  If you work at a law office, or a hamburger stand, or a school, or anything you like, does your boss ever say "Here is your paycheck for $5000.  I know you only earned $1000, but I'm just going to give you the whole $5000, and you're supposed to use $4000 of it to pay your coworker Joe his wages."  No.  There is no reason to do that except that the "other mystery shopper" is actually the scammer.