Net working capital represents the money tied up in the daily operations of the business. This includes both current assets and current liabilities.
On the current assets side, we typically include accounts receivable, inventory, and prepaid expenses as part of net working capital. All these items will tie up cash, but are generally necessary for the operation of the business. For example, accounts receivable will tie up cash because customers are paying with credit rather than cash.
Note that cash is not included. This is because cash is not being used in the daily operation of the business. It is simply cash that is sitting unused. Similarly, deferred tax assets are not included because tax assets ar an accounting / tax matter, and do not impact the daily operation of the business.
On the current liabilities side, we typically include accounts payable and other current liabilities. Deferred tax liabilities are not included as that is an accounting / tax matter.