Employers with 50 or more employees must file employee starting and leaving forms, P45 and P46, and the new forms P46 (Pen) and P46 (Expat) online from 6 April 2009. If a return is filed on paper when it should have been filed online, then HMRC may apply a penalty.

Employers with fewer than 50 employees will have to file these in-year forms online from 6 April 2011.

HMRC have also introduced two new in-year forms from April 2009.

From 6 April 2009, form P46 (Pen) replaces the old form P160 and PENNOT electronic information. From that date, employers must use the new form if pension payments to an employee are commenced for the first time. In other words the form P46 (Pen) must be used for all new pension payments.

In addition from 6 April 2009 a form P46 (Expat) must be used instead of a standard form P46 for the following categories of employee seconded to work in the UK:

• individuals working wholly or partly in the UK for a UK-resident employer on assignment while remaining employed by an overseas employer
• individuals assigned to work wholly or partly in the UK at a recognised branch of their overseas employer's business
• individuals included in an employer's dedicated expatriate PAYE scheme
• individuals included in an employer's expatriate modified PAYE scheme

Full details of these new forms and the required online filing of in-year employer's forms are available at http://www.hmrc.gov.uk/paye/file-or-pay/fileonline/tasks/in-year.htm#2