To avoid paying late you must make sure HM Revenue & Customs (HMRC) have cleared funds by the due date. If you pay electronically the due date is the 22nd of the month following the end of the tax month, or quarter to which it relates.
For 2012-13, PAYE month 03 - or quarter 1 - period ended 5th July 2012, the due date is Sunday 22nd July 2012.
Additionally for 2011-12, Class 1A NICs, the due date is Sunday 22nd July 2012.
HMRC must receive cleared funds by Sunday 22nd July 2012.