Introduction
Commercial banks and central banks have different roles in the money supply process. While the central bank has the sole right to issue currency, commercial banks create money through the process of lending.

Money Creation by Commercial Banks
When a commercial bank lends money, it creates new deposit balances in the borrower's account. These new deposits are considered as money since they can be used for transactions and are part of the money supply. The process of money creation by commercial banks is known as credit creation or deposit expansion. When banks lend out a portion of their deposits, they create new deposits and expand the money supply.

Central Bank's Role in Currency Issuance
While commercial banks create money through lending, they do not have the authority to issue currency. The central bank, on the other hand, has the sole right to issue currency. The central bank controls the money supply through its monetary policy by influencing the amount of money in circulation. It can increase or decrease the money supply by either buying or selling government securities or by changing the reserve requirements of commercial banks.

Impact of Money Creation on National Income
Money creation by commercial banks has a significant impact on national income. When banks create new loans, they inject new money into the economy, which leads to an increase in aggregate demand. This increase in demand can lead to higher economic growth and increased employment opportunities. However, if the money creation process is not managed properly, it can lead to inflation and instability in the economy.

Conclusion
In summary, both commercial banks and central banks play important roles in the money supply process. While commercial banks create money through lending, the central bank has the sole right to issue currency. Money creation by commercial banks has a significant impact on national income, and it should be managed carefully to ensure the stability of the economy.