Pension sharing orders need to be formally applied for and approved by the court. This can be done by completing a Form A and sending this to the court (together with the court fee).
Completing a Form A means you're asking the court to deal with your dispute. A court timetable will be put in place and will follow a series of steps and hearings that both you and your ex will need to comply with or attend. Before completing a Form A, you should speak to a specialist family lawyer to understand the options open to you.
Many couples do come to an agreement about splitting their pensions outside of the courtroom. This means they only need a consent order from the court, which approves that agreement. Either way, without a court order, the pension scheme provider is unable to implement a pension sharing order.