Free one year renewal with domain transfer?

[humptydumpty]

Happy new year everyone! Many registrars offer one year renewals when you transfer a domain to them. I never got that to work and was wondering if anyone knows how it works exactly. I’m unlocking the domain, getting the transfer code, paying for one year with the new registrar but the expiration date is always one year later, not two!

I usually transfer domains within the last 30 days before expiration if that makes a difference. The extension is .com.