"Depreciation expense is the most common non-cash expense, as the cash is spent upfront and then expense is recognized over the life of the asset. Amortization expense is another example, and it is most commonly associated with items such as software, intangible assets and long-term contracts. It's important for a bookkeeper to be familiar with these items, as they are added back to net income on the statement of cash flows."

Non-cash expenses are expenses that are not related to cash. Even if they're reported in the income statement, they have nothing to do with cash payments. The most common form of non-cash expenses is depreciation. Other examples are amortization, stock-based compensation, and unrealized gains and losses.