账期内有效，英文为“Valid within the accounting period”。

在财务管理中，账期指的是一个特定的时间段，通常为一个财务年度或一个经营周期。在这个时间段内，企业的经济活动和交易都会被记录和核算。而账期内有效，则指的是某个事项、交易或活动只有在特定的账期内才具有效力和意义。

例如，在企业的销售业务中，经常会遇到退货的情况。为了确保销售收入的准确性和完整性，企业通常会制定退货政策，规定退货的有效期，即只有在特定的账期内退货才被接受并允许冲减销售收入。如果超过这个账期，退货将不再被接受，已确认的销售收入也不会被冲减。

此外，账期内有效还常用于企业评估和管理内部流程和绩效。例如，在评估员工的工作表现时，通常会以一个特定的账期为基准，对员工在该账期内的业绩进行评价和奖惩。这种评价方式能够更准确地反映员工的实际工作表现，也能激励员工在未来的工作中更好地发挥自己的能力和潜力。

总的来说，账期内有效是一种财务管理和绩效评估的常用概念。通过明确账期和账期内有效的规定，企业能够更好地管理和规范自身的经济活动和业务流程，确保财务信息的准确性和完整性，并为企业的决策和发展提供有力的支持。

英文对照：

In financial management, the term "accounting period" refers to a specific time period, usually a fiscal year or an operating cycle. During this time period, the economic activities and transactions of the enterprise are recorded and accounted. The term "valid within the accounting period" means that a certain matter, transaction or activity is only valid and meaningful within a specific accounting period.

For example, in the sales business of an enterprise, returns are often encountered. In order to ensure the accuracy and integrity of sales revenue, an enterprise usually formulates a return policy, specifying the effective period of returns. That is, only returns accepted within a specific accounting period are allowed to reduce sales revenue. If超过这个账期，退货将不再被接受，已确认的销售收入也不会被冲减。

In addition, "valid within the accounting period" is also often used in enterprise evaluation and management of internal processes and performance. For example, when evaluating employees' performance, it is usually based on a specific accounting period to evaluate and reward or punish employee performance during that period. This evaluation method can more accurately reflect employees' actual work performance, and also encourage employees to better发挥自己的能力和潜力in their future work.

Overall, "valid within the accounting period" is a commonly used concept in financial management and performance evaluation. By specifying the accounting period and the rules of "valid within the accounting period", an enterprise can better manage and standardize its economic activities and business processes, ensure the accuracy and integrity of financial information, and provide strong support for enterprise decision-making and development.