Before you can start maternity leave, you need to provide your employer with at least two weeks notice. You also need to provide medical documentation confirming your pregnant status. Should you decide to take the additional 16 weeks leave, you need to give your employer at least four weeks' notice. If you prefer, both these notices can be handed over at the same time.
Early birth – more than four weeks early – means you need to provide your employer with notice for leave within 14 days of delivery. Doing so will make your notice period legally compliant.
If your doctor prescribes that you need to start maternity leave for medical reasons, the earlier date on your medical certificate applies. Doing so deems you compliant with the notice requirements, as is described in Section 11 of the Maternity Protection Act 1994.
Your employer needs at four weeks' written notice of your intended date to return to work. All notice requirements need full compliance. Failure to comply with them, may affect your rights and benefits. Remember to inform your employer of your intention to postpone your maternity leave; bear in mind that your employer can refuse your application.