The most important assumption governing financial statements under the conceptual framework is the going concern assumption. The going concern assumption assumes that the entity will continue to operate in the foreseeable future, without the need to liquidate its assets or reduce its operations.

This assumption is important because it forms the basis for the preparation of financial statements, and it affects the way that assets, liabilities, revenues, and expenses are recognized and measured. Without the going concern assumption, assets and liabilities would need to be measured at their liquidation value, rather than at their current value, and revenues and expenses would need to be recognized on a cash basis, rather than on an accrual basis.

The going concern assumption also affects the presentation and disclosure of financial statements, as it requires entities to provide information about their ability to continue operating in the foreseeable future. If an entity's ability to continue operating is in doubt, this must be disclosed in the financial statements, and the financial statements may need to be prepared on a different basis, such as a liquidation basis.

Overall, the going concern assumption is essential for the preparation of meaningful and useful financial statements, as it allows entities to present financial information on the basis of their ongoing operations and provides stakeholders with information about the entity's ability to continue operating in the foreseeable future.