Political parties have to compile financial statements (so-called accountability reports) on their finances on an annual basis. This obligation exists whether political parties receive funding or not. Each political party must have its report audited and signed by two chartered accountants. The Austrian Court of Audit appoints these chartered accountants for a period of five years. The political parties must submit their accountability reports of the respective previous year to the Austrian Court of Audit each year by 30 September.
Please find the political parties' accountability reports, broken down by year, here (in German).