From 6 October 2014, HMRC were due to start fining employers who submitted their RTI report (essentially an online report saying "this is how much we're going to pay our employees, and this is the tax and NI we'll be paying to you") late. This had already been delayed once, and now it's been delayed again - for employers with 50 staff or fewer anyway - until the slightly strange date of 6 March 2015 (why not just wait until 2015-16?).
This is largely being greeted in the tax industry as excellent news. To be honest, it's almost certainly going to happen some time in the next year or two, so if the system that will assess and enforce the penalties is working they might as well just get on with it so everyone get to grips with it. One suspects that the system probably isn't working, though, hence the further delay. In any case, our experience of RTI so far has been that it isn't problematic for an organised employer to make the reports on time, or to arrange for their accountant/payroll provider to do it, so when the regime is enforced, responsible employers shouldn't have to worry. In most cases, if an employer is having trouble working out by payday how much they're supposed to pay staff, and how much PAYE is payable, then there's an underlying problem that RTI has simply brought to the surface!