Do they have a minimum buying amount I sure I read that somewhere.
No. There is a flat $0.15 fee for the ACH however, which would make a $0.28 transaction sound as if OP bought 12 cents of BTC, plus 1% fee plus the flat fee, for a >100% total markup. Kinda silly but I could see testing the process with small amounts.
This is a problem between your bank and CoinBase. It's not so much about you as it is with certain banks flagging any transaction to CoinBase...
Switch your bank with one who is friendly with BitCoin and your account won't be high risk.
The "High Risk" is an indication that your bank flagged the withdrawal.
This is a myth. There is no banking apparatus around ACH for this. OP, did they transfer your money and then return it, or decline it basically immediately?
Small test transactions often get flagged by fraud detection algorithms.
This is factual. That said, ACH is used for test deposit verification all the time.
...if the xfer declined within a fee minutes, it's CB's real fraud algorithm. If it declined after a day or two, the bank could have stopped it — but CB would see it as no different than an NSF, and any communication between them and a bank regarding actual fraud would forbid them legally from saying it was suspected fraud. They said it was their internal fraudbot so that's out.
I'd be amused to find out they transferred and returned it. That's their other "fraud" algorithm. Never heard of it for small amounts like this, though. But bugs will be bugs.
