Final answer:
The least helpful financial ratio for identifying a company's financial difficulties is net income before taxes/net sales, as it does not directly indicate the firm's ability to meet financial obligations, unlike other ratios that address solvency and liquidity.
Step-by-step explanation:
Among the provided financial ratios, the one that is least likely to assist an auditor in determining whether a client is experiencing financial difficulties is net income before taxes/net sales. This ratio, also known as the profit margin, provides information on the company’s operational efficiency and profitability but does not directly reflect the company’s ability to meet its financial obligations. A company might have a good profit margin yet still experience financial difficulty due to a high level of debt or poor cash flow management.
In contrast, ratios like net worth/total liabilities, cash/total assets, and total liabilities/total assets give clear insights into the firm's solvency, liquidity, and capital structure, which are critical when analyzing potential financial difficulty. For instance, a low net worth compared to liabilities or high liabilities compared to assets can indicate a higher risk of financial distress.