Hi Maura Masi,
If your U1 form has been processed, we issue all replies by postal methods as they are official certificates. Delivery can take 4 to 6 weeks to be received overseas and 1 to 3 weeks if it is to a UK address.
The international caseworker department can advise you of the correspondence issue date and any issues going forward regarding the U1.
National Insurance: general enquiries
Thank you.