The deadline for most applicants was June 30th. If you missed the deadline, you may still be able to apply. See: late applications.

There are special provisions for people who have a PR card or another document issued under EEA Regulations.

Page 43 of the EUSS Guidance says:

Document or status under the EEA Regulations

Where a person subject to the 30 June 2021 application deadline for EEA citizens and their family members resident in the UK by the end of the transition period has a biometric residence card or other residence document issued under the EEA Regulations which remains valid at that date, they may not realise that, with the end of the grace period, they can no longer rely on an EU law right of residence in the UK and need to obtain UK immigration status under the EU Settlement Scheme.

They can make a late application to the scheme where you are satisfied, in line with this guidance, that there are reasonable grounds for them missing the 30 June 2021 deadline, e.g. because they were not aware that they needed to apply to the EU Settlement Scheme.
You need to apply for settled status even if you have a valid PR document.

A PR document can be:

A PR certificate inside your blue or pink card holder;
A certificate inside your passport;
A biometric card confirming Permanent Residence (not a Residence Card).

EEA and Swiss nationals get a "Document Certifying Permanent Residence"

Biometric residence cards for non-EEA nationals say ‘Permanent Residence Status"

PR documents will no longer be valid after the end of June 2021.

However, you can still use them to make a late application under the provisions above.

Registration Certificates, Residence Permits and Residence Cards are NOT PR documents.

The EUSS form has the following question:

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If the answer is Yes, you are prompted to enter the document number. This is the number on the document INSIDE the blue card holder.

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If you cannot provide the PR document number, for example, because the number is damaged or obscured, or the document never had one, the Home Office will check its own records. If there is no record they will contact you for further details such as approximate date of issue. If there is still no trace, you will have to submit the document for consideration.

If it is identified that you do not satisfy the requirement of not having been out of the UK for 5 years or longer after the issue of your PR document, you will not get settled status on this basis.

You may still be able to apply via a different route, or get pre-settled status.