There is no point of discussing whether Riba (interest) is Halal or Haram according to Islamic teachings. Majority of Islamic Scholars around the world has declared conventional banking against Shariah and there are many Fatwas given by Muftis around the globe. Below are some excerpt taken from couple of articles to explain the mechanism of Islamic Banks and practically how they are operating within the boundaries of Shariah.
The basic principle of Islamic banking is the sharing of profit and loss and the prohibition of riba(usury). Common terms used in Islamic banking include profit sharing (Mudharabah), safekeeping (Wadiah), joint venture (Musharakah), cost plus (Murabahah), and leasing (Ijarah).
In an Islamic mortgage transaction, instead of loaning the buyer money to purchase the item, a bank might buy the item itself from the seller, and re-sell it to the buyer at a profit, while allowing the buyer to pay the bank in installments. However, the bank’s profit cannot be made explicit and therefore there are no additional penalties for late payment. In order to protect itself against default, the bank asks for strict collateral. The goods or land is registered to the name of the buyer from the start of the transaction. This arrangement is called Murabaha. Another approach isEIjara wa EIqtina, which is similar to real estate leasing. Islamic banks handle loans for vehicles in a similar way (selling the vehicle at a higher-than-market price to the debtor and then retaining ownership of the vehicle until the loan is paid).
An innovative approach applied by some banks for home loans, called Musharaka al-Mutanaqisa, allows for a floating rate (interest ratethat changes on a periodic basis) in the form of rental. The bank and borrower form a partnership entity, both providing capital at an agreed percentage to purchase the property. The partnership entity then rents out the property to the borrower and charges rent. The bank and the borrower will then share the proceeds from this rent based on the current equity share of the partnership. At the same time, the borrower in the partnership entity also buys the bank’s share of the property at agreed installments until the full equity is transferred to the borrower and the partnership is ended. If default occurs, both the bank and the borrower receive a proportion of the proceeds from the sale of the property based on each party’s current equity. This method allows for floating rates according to the current market rate such as the BLR (base lending rate), especially in a dual-banking system like in Malaysia.
There are several other approaches used in business transactions. Islamic banks lend their money to companies by issuing floating rate interest loans. The floating rate of interest is pegged to the company’s individual rate of return. Thus the bank’s profit on the loan is equal to a certain percentage of the company’s profits. Once the principal amount of the loan is repaid, the profit-sharing arrangement is concluded. This practice is called Musharaka. Further, Mudaraba is venture capital funding of an entrepreneur who provides labor while financing is provided by the bank so that both profit and risk are shared. Such participatory arrangements between capital and labor reflect the Islamic view that the borrower must not bear all the risk/cost of a failure, resulting in a balanced distribution of income and not allowing lender to monopolize the economy.
Source:
http://www.islamicmortgages.co.uk/index.php?id=269
http://www.gamji.com/article6000/NEWS7908.htm
http://www.islamweb.net/emainpage/index.php?page=articles&id=135434