MAT B1 is the medical evidence given to the employee by the
doctor or midwife showing the expected date of confinement
(childbirth). Evidence is acceptable if it is signed from the start
of the 20th week before the EWC.
The employee must produce medical evidence of the date the baby is due, usually the MAT B1, but the employer can accept other medical evidence providing it shows the date the baby is due.
For details of rules for giving employer medical evidence of EWC see SPM20500.