I started paying the CSA october 2010, when do they reassess.?

hi i started paying the csa october 2010, i should be paying �160 per month but was in arrears of �160 so they spread it over the 11 months so im now paying �174 per month. what i want to know is will they reassess me when october comes as it will be a year or will they do it at anytime, why im asking is because iv been doing overtime and was going to stop the overtime 3 months before october incase they want 3 months payslips. also iv found out that my ex has just been given 20 thousand pounds so is there anyway i can tell the csa about this because i know she wont have declared it. thanks. carl