Grace period vs redemption period
An expired domain does not disappear on its expiry date. It moves through stages, and the difference between them is the difference between an inconvenience and several hundred dollars.
Grace period
Typically 0–45 days after expiry, at the registrar's discretion. The domain stops resolving — your site is down and your mail is bouncing — but you can renew at the normal price.
Length varies by registrar and TLD, and it is not guaranteed. Some registrars offer none.
Redemption period
Typically 30 days after the grace period. The registry has flagged the domain for deletion. You can still recover it, but only via a redemption fee that is commonly $80–200 on top of the renewal, and the process is manual and slow.
Pending delete
5 days. Nothing can be done. At the end the domain is released, and for a valuable name there are services whose entire business is being first in the queue.
Why this matters for monitoring
The whole sequence starts on a date known months in advance, and the usual cause of missing it is that the registrar's renewal notices go to an address nobody reads any more — a colleague who left, or the inbox of an agency that stopped working with the client two years ago.
That is the failure IT Watch's renewal ownership register exists for: recording who can actually renew a domain, alongside the date it comes due.
Related
Check any domain's expiry date with the WHOIS lookup tool.
See also: Registrar lock.