Internal financial statements are statements that answers the needs of the internal readers, consequently, does not necessarily answer the needs of readers outside the company, like banks or CRA. Therefore, they likely do not follow any accounting standards. Their goal, is to provide information of a given period in a way that it pulls specific data to help make decisions. For example, you could have a set of financial statements that includes an income statement that shows the current period, year to date, compared to the prior year as at the closing date, or you could have a set of financial statements that shows an income statements and a balance sheet with every months comparing a month to the previous year. Their isn't any specific rules to internal financial statements, as long as they are easy to read and provides the data you require to make strategic decisions.