At present you can recover Statutory Sick Pay (SSP) amounts that are in excess of 13% of your total employee and employer Class 1 NICs liability for the month in question.
However, small employers will no longer be able to reclaim any SSP from HMRC from 6th April, as the Percentage Threshold Scheme for recovery of SSP is being abolished from 6th April 2014. Employers will have until April 2016 to recover SSP for 2013-14 and prior years.