The Stocks and Shares ISA deadline (6 April) is rapidly approaching. This means an investor who doesn’t use their full £20,000 allowance for this tax year will lose it forever.

Given the enormous tax benefits of the ISA — not a penny is due to HMRC on capital gains or dividends — any failure to ‘max out’ the full allocation can really hit you in your pocket. At this time of year, I’m looking to put as much money in my own account as possible.

That doesn’t mean I have to buy any stocks, trusts or funds right away. Just making the deposit itself is enough to secure this year’s allowance. But why wait? There are stacks of bargain shares on the FTSE 100 alone to choose from. Some look even more tasty from a value perspective following recent stock market volatility.

Here’s one dirt cheap FTSE share I think deserves serious attention today.

Silver surfer

Fresnillo (LSE:FRES) is the world’s biggest sliver producer, as well as a significant gold supplier. As such, its shares have taken off as precious metals have exploded. It’s risen a spectacular 334% in value in the last year alone.

Yet today, Fresnillo’s share price still offers stunning value. At £36.96 per share, the company trades on a forward price-to-earnings growth (PEG) ratio of 0.4. Earnings are tipped to surge 46% year on year in 2026.

A reminder that a PEG ratio of 1 implies a share that’s undervalued. So why is the FTSE 100 company trading so cheaply?

It could be that the market fears gold and silver prices could remain volatile following their recent stunning gains. It’s also worth remembering that mining for metals is extremely unpredictable business.

Even if bullion prices keep rising, a company’s share price can sink if it endures exploration, mine development or production issues. These can leave earnings projections in tatters.

Can Fresnillo shares keep rising?

Yet on balance, I think the potential rewards of buying Fresnillo shares could offset these dangers. It’s why I think the Latin American miner’s worth serious consideration this ISA season.

First off, the £28 billion-cap company has enormous scale that helps it absorb localised operational issues. It has eight working mines in Mexico and a string of advanced development and exploration projects spanning The Americas. If one project experiences problems, it doesn’t knock the group as a whole out of sync.

This leaves it better placed to exploit the long bull run in precious metals. The question is, can gold and silver keep soaring? I think they can, as safe haven demand from central banks and investors marches ever higher.

Inflows into gold-backed exchange-traded funds (ETFs) soared again in February, according to the World Gold Council. This resulted in the strongest ever two-month start to a calendar year. With geopolitical tensions increasing and inflation fears growing too, I expect Fresnillo shares to keep heading higher, giving ISA investors a boost.