When you buy bitcoins, the seller is using a wallet to transfer the ownership of the coins to you. Currently, the U. Altcoins are traded globally on hundreds of exchanges. Deposits can be made through bank transfer, SEPA transfer, international bank wire, and now even credit cards. Chapter 3 Payment Methods. Any service that claims to pay interest on bitcoins or increase your bitcoins is likely extremely risky or an outright scam. Every 4 years, the bitcoin halving happens where the new supply rate is cut in half.