Until the midnight on the 5th of April you can buy extra years as far back as 2006.
Sorry - not read whole thread just initial post - but we’ve just had a Martin Lewis special on TV.
Ultra-important for people buying back years.
There is a potentially unbeatable opportunity everyone aged 40 to 73(ish) needs to consider. You’ve got until 5 April 2025 to buy back any missing National Insurance years from 2006 to 2016. This can be prove very lucrative, as some are on course to make over £50,000 in boosts to their State Pension by following this guide.
https://www.moneysavingexpert.com/savings/voluntary-national-insurance-contributions/
Luckily myself and wife have done our time! So France - here we come :-).
Fair enough.
I was relaying my actual experience last July. I guess my situation was different for some reason, or the rules got changed (again).
However, here’s what is on the HMRC site at the moment…
From the 6th of April you can only pay for gaps relating to the past 6 tax years, so as it was before.
Here in the UK there has been a massive publicity campaign to get people to pay more attention to their state pension entitlement and make additional contributions where necessary. The campaign has been so successful that HMRC cannot cope with the demand hence the huge backlogs and difficulty in speaking to someone.
Yes, despite having had exchanges with HMRC back in July 2024 & paying the correct top up money my pension record has still not been updated…!
I did manage to talk to someone there a month or so ago who assured me that they had the money & that my ‘upgrade’ would happen as they had received all the info & money ahead of the 05/04/2025 deadline.
They were still citing Covid restrictions as being the cause of all their backlogs 
As I’ll be able to claim my UK OAP from next February I’d quite like to see the record updated before I apply. Fingers are crossed.
EDIT - sorry, I see Larkswood has already answered this question above.