People often ask the question “when should I transfer my domain?” And that usually regards to transferring to another domain registrar to renew and just leave the old one. Some people think its good to do it the day before it expires and that is a very, very bad idea. Some registrars won’t let you do it if it’s less than 5 days to expiration.
I would suggest you do it a month ahead of time. Don’t worry you won’t lose a month of registration, it’ll just be added on. This is Another misconception among domain owners. It can take up to 10 business days for a domain to transfer between registrars so you have to give it time to do that. If you do it a week before, you could have waited too long and the domain will just expire before transfer is even fully initiated.