Informal arrangement. Initially via Minute of Agreement but that was in 2007 and, as he is self employed, he has altered payments on numerous occasions since this date. When he was constantly changing/reducing payments I suggested we go through the CSA to make a more formal agreement. My ex said if I proceeded down this route he would declare minimum income (he is registered as a single share holder of his company). This would work out a lot less in maintenance payments so I decided to continue as we are.