Is this a scam?
Bad Check Scam (if it is a check). For example: If the person were to mail a "bad check" to you and you cashed it to give money to other people, the bank will soon see it is a bad check and put your account in negative. Same thing with the mystery shoppers scam: You get a letter in the mail inviting you to be a mystery shopper. You reply by calling or something, they then send you a $1,000 check (The check is actually "bad" without you knowing). They tell you cash it at your bank, keep $200 to pay for your shopping trip, but send the remaining $800 in gift cards to mail to them or wire transfer to the secret shoppers scammer. Next thing you know, the bank let's you know the check you cashed was "bad". The bank wants $1,000 plus overdraft fees. You have the $200 you kept for doing shopping. But you're out of alot of money as the scammer got $800. DO NOT TAKE CHANCES ON MYSTERY SHOPPING, or any scam that involves cashing a check and sending some money back to the scammer.
The money going into your account is really from stolen credit cards. You can take it out and send it to him. A few days later the bank realised the card is stolen and reverses the deposit in your account. So if you have any money in your account it will be taken back. If you don't you will go into the red and get extra charges.
Yes, that is a scam. He will lie to you until you send him some money.
There's no tax on deposits, scam.