Unless they act before the end of the tax year on April 5, they could miss out on a big opportunity to top up years of state pension that may otherwise be lost for good.

Some could lose pension worth tens of thousands of pounds over their retirement.

People are waking up to the danger and hundreds of thousands are scrambling to beat the fast-looming deadline.

Yet as I found out myself, government hotlines designed to help people work out what to do are sinking under the weight of calls.

Anybody who believes they are heading for a state pension shortfall at retirement should check their position immediately, as there is no time to waste.

Most of us build state pension entitlement by making qualifying National Insurance (NI) contributions during our working lifetimes.

This is done automatically through PAYE or a self-assessment tax return.

Those who have made 35 years of NI contributions should get the maximum new state pension, paid to those retiring after April 6, 2016.

But many, especially women, end up with gaps after taking time off to raise a family or care for loved ones.

Others lose out because they have an illness or disability, are unemployed, or are self-employed but not earning enough money to pay NI.

I have a gap because of time spent living and working overseas.

In many cases the gap will automatically be plugged with National Insurance credits, but not everyone qualifies.

Those who do not can buy extra state pension by making voluntary Class 2 or Class 3 NI contributions.

As I have written before, they will get a fantastic return on their money. But only if they get their act together.

I've filled in my forms and now I'm waiting for the verdict, but I'm worried that call centre staff are so hard pressed they won't get all the applications done in time.

So don't hang about if you think you qualify. The longer people delay and the closer that deadline looms, the greater the chance of missing out on this once-in-a-lifetime opportunity.

Making voluntary NI contributions will not work for everyone but those in the following position you should consider it.

You’re close to state pension age and do not have enough qualifying years to get the full state Pension.

You will not be able to get the qualifying years you need to get the full state pension during your working life.

You’re self-employed and file self-assessment tax returns but do not have to pay Class 2 NI contributions because you have no profits.

You live outside the UK, but still want to contribute towards your state pension.

If any of these apply to you, visit the Future Pension Centre website or pick up that phone. Just be prepared for a lengthy wait.