A tax audit can be initiated by some problems with the tax return and it can be randomly select a tax return for an audit. There are a number of checks and balances and if any of them raise a red flag, they come knocking on your door.You can visit http://www.highburytaxsolutions.com in order to get more information about an audit.
One of the reasons for the audit is that the reported income is different from what CRA found out from their other sources. For instance, when you forget to include your earnings from a saving account.
Your bank reports this information to the CRA and they will contact you to find out why the figures differ. They will inform you, that they made changes to the tax return. They will give you the option either to accept the changes or to dispute.
In some rare cases, you should accept it, but it often happens that CRA makes mistakes and you must fight for your money. Most such cases are easy to resolve.
On the other hand, many audits are fairly harder. They may question the cogency of your business expenses or other amortizations. A professional help is required to prove that your expenses were necessary or the changes, that the CRA had made, were incorrect.
In such cases, a letter to the CRA will not be enough to defend you. The best choice is to hire a tax audit specialist to protect your money.