Okay, let’s start at the beginning. If you want accurate advice on this you should not go to either the HMRC or gov.uk web sites. The former is convoluted. The latter is simplistic and veers between misleading, insufficiently detailed or just plain wrong. Similarly phone calls to either organisation are a waste of time.
Firstly they are sufficiently understaffed that the average wait time is something like 35 minutes for an average 8 minute call duration. These are averages. The general experience is that you either give up or are waiting around 65 minutes. The recommendation is to ring between 9:30am and midday. In my experience that can make a difference but it’s generally a small one.
Secondly, the majority of calls are now outsourced. The call handlers have a set number of scripts and if your query veers even slightly off script then you get what I call “call centre crack” as in “crack cocaine”. This is characterised by the inability to use the phrase “I am sorry. I do not know.” matched only by the equal desire to say “something” in order to appear credible and in order to record a stat saying you have answered the query no matter how much BS then comes out of your mouth. It’s really important to understand that these conversations can be incredibly detailed and credible… but absolute total BS.
In this context it’s important to note that neither HMRC nor DWP have an advice function i.e. technical staff with training on the law, guidance and current case law and an obligation or duty of care to provide accurate advice. Neither are advice services and if you are daft enough to rely upon anything said by them then it’s very much at your own risk.
The most important thing to note here is that you can top up to the basic SRP (State Retirement Pension) amount if you are short but if you are currently entitled to that amount then there is no further top up available. There was previously a scheme which opened in 2015 and closed in 2017 but at present the only gain in making voluntary contributions is if you have an actual deficit or if you think it likely you will need to rely upon other contribution based benefits for a period. There is now only contribution based JSA or ESA and, frankly, the circumstances in which the amount of money you’d need to pay voluntary contributions to get those potentially relatively short and very low entitlements means that the circumstances in which it would be worthwhile are very limited.
The number of instances I have come across in work over the years of people who have made voluntary contributions only to discover they have depleted their capital for zero gain beggars belief. To reiterate, this is worth it (possibly) if you have a shortfall but it is anything but a “no-brainer”. If you already have your years in and an entitlement to the maximum pension then you are essentially throwing money away.
You may well ask why neither HMRC nor DWP will stop you doing this. Essentially you’re giving them money so they won’t say “please don’t” but also they will take the view, without examining it in detail, that you could be filling in gaps in order to qualify for contribution based JSA or ESA. The third reason is of course that the staff are now so unqualified that they have neither the ability nor inclination to say “actually you simply don’t need to do that”. It’s a thoroughly dispiriting state of affairs.
If you think there is a reason to do this I strongly recommend you get a pension forecast; get a breakdown of your NI record (what you think it is can often be miles away from what records suggest it is) and then seek advice from Citizens Advice, your local authority welfare rights service or an independent advice centre such as an Unemployed Workers Centre or a Law Centre. Literally the only places likely to have the expertise you need to understand your options and make an informed decision.
@Fatcat you are correct re: the 6 year limit but there is an exception to this which allows gaps between 06 and 16 to be filled if you’re a man born after the 5th of April 1951 or the 5th of April 1953 if you’re a woman. Again though it may not be automatically the best thing to do so… get advice.