The Australian Taxation Office has revised its data for borrowing by self-managed superannuation funds, revealing that the SMSF loan market is much bigger than previously understood.Assets held by SMSFs under limited recourse borrowing arrangements have been revised from A$9.3 billion to $15.1 billion for the June quarter in 2014.The ATO's estimate for SMSF assets held under borrowing arrangements in the June quarter this year is $15.6 billion, representing about three per cent of assets held by SMSFs.The ATO said in a media release: "The increase can be attributed to some growth in the use of LRBAs by SMSFs and improved data collection through new LRBA asset labels on the SMSF annual return."The ATO said it was confident the revised figures provided a more accurate reflection of SMSF exposure to borrowing.Self-managed fund trustees have been able to borrow since 2007. A loan can only be used to acquire a single asset, it must be limited recourse and the asset must be held in a separate trust until it has been paid for.The emergence of LRBAs has been controversial, with some commentators arguing that borrowing exposes super funds to unnecessary risk. Only a minority of lenders offer the product.The Financial System Inquiry agreed with this view and recommended that SMSF borrowing be banned. The Government is yet to respond to that recommendation.According to the ATO, in the June quarter there were 557,000 SMSFs with total assets of $590 billion. Both the number of funds and their assets increased by around six per cent, compared with the previous corresponding period.