Stocks and Shares ISA in the red? Here’s how I’d react

After seeing the value of some holdings in his Stocks and Shares ISA crash, our writer reflects on how he could react as a long-term investor.

The content of this article was relevant at the time of publishing. Circumstances change continuously and caution should therefore be exercised when relying upon any content contained within this article.

Mindful young woman breathing out with closed eyes, calming down in stressful situation, working on computer in modern kitchen.

Image source: Getty Images

You’re reading a free article with opinions that may differ from The Motley Fool’s Premium Investing Services. Become a Motley Fool member today to get instant access to our top analyst recommendations, in-depth research, investing resources, and more. Learn More.

It can be alarming to invest money hoping to see it increase only to see it disappear. That happens to most investors at some point, as markets go down as well as up. Sometimes, looking at my Stocks and Shares ISA, I see its value is in the red. That could be alarming – so here is what I do.

Understand paper losses

Stock markets move up and down, as do individual shares. The valuation of a portfolio, such as that held in a Stocks and Shares ISA, is usually a snapshot of the money I would expect to get if I sold the shares today. But if I do not sell, a negative valuation is only what is known as a paper loss.

As the name suggests, it exists on paper (or a screen). If I sold at the current price, I would make a loss. But I can keep owning the shares and doing nothing. If they move up in price, my ISA may move into the black again. Then again, they might not recover. Shares that fall can keep falling.

A valuation is a summary of what the whole universe of investors thinks my portfolio is worth right now. I actually think that is valuable information for me to have even if it makes for difficult reading. Indeed, it might lead me to re-evaluate some of my investment decisions. Crucially though, the paper loss does not mean I have actually lost money — unless I sell the shares at such a price.

Revisiting investment cases

But imagine that a share in my ISA is showing a huge loss – maybe it is 50%, 70% or even 90% lower in price than when I bought it.

Although that does not mean I have actually lost money if I have not sold any shares, it certainly would grab my attention. Imagine a share fell 90%? Sadly I do not need to imagine this, as the past year has seen the share price of my holding Renalytix tumble 89%. So basically, if the market reckons a share is worth just one tenth of what I paid for it, what does that tell me about its valuation?

Reshaping my Stocks and Shares ISA

Either I have overvalued it, or the market overall is undervaluing it. We cannot both be right.

Therefore, a large fall could be a trigger for me to revisit the investment case for a particular stock. If things have changed that affect how I value a share, such as a worse profit outlook, maybe I will think the price drop is justified. In that case I may decide whether I want to keep holding the shares, or act on the changed investment case and sell at a loss. Doing the latter can be painful, but less costly than selling at an even bigger loss further down the line.

What if I think nothing fundamental has changed in the investment case but the shares are now much cheaper than they were? In that case, I may decide to use the price drop as a buying opportunity to add to my position, while never letting any one single share become too dominant in my ISA.

Christopher Ruane owns shares in Renalytix. The Motley Fool UK has no position in any of the shares mentioned. Views expressed on the companies mentioned in this article are those of the writer and therefore may differ from the official recommendations we make in our subscription services such as Share Advisor, Hidden Winners and Pro. Here at The Motley Fool we believe that considering a diverse range of insights makes us better investors.

More on Investing Articles

Young female business analyst looking at a graph chart while working from home
Investing Articles

Down over 30% this year, could these 3 UK shares bounce back in 2026?

Christopher Ruane digs into a trio of UK shares that have performed poorly this year in search of possible bargains…

Read more »

Mature people enjoying time together during road trip
Investing Articles

Yields up to 8.5%! Should I buy even more Legal & General, M&G and Phoenix shares?

Harvey Jones is getting a brilliant rate of dividend income from his Phoenix shares, and a surprising amount of capital…

Read more »

Light trails from traffic moving down The Mound in central Edinburgh, Scotland during December
Investing Articles

Up 7.5% in a week but with P/Es below 8! Are JD Sports Fashion and easyJet shares ready to take off?

easyJet shares have laboured in 2025, but suddenly they're flying. The same goes for JD Sports Fashion. Both still look…

Read more »

US Stock

I think this could be the best no-brainer S&P 500 purchase to consider for 2026

Jon Smith reveals a stock from the S&P 500 that he feels has the biggest potential to outperform the index,…

Read more »

Surprised Black girl holding teddy bear toy on Christmas
Investing Articles

Up 20% in a week! Is the Ocado share price set to deliver some thrilling Christmas magic?

It's the most wonderful time of the year for the Ocado share price, and Harvey Jones examines if this signals…

Read more »

Close-up as a woman counts out modern British banknotes.
Investing Articles

I asked ChatGPT for the 3 best UK dividend shares for 2026, and this is what it said…

2025 has been a cracking year for UK dividend shares, and the outlook for 2026 makes me think we could…

Read more »

Storytelling image of a multiethnic senior couple in love - Elderly married couple dating outdoors, love emotions and feelings
Investing Articles

£10k invested in sizzling Barclays, Lloyds and NatWest shares 1 year ago is now worth…

Harvey Jones is blown away by the performance of NatWest shares and the other FTSE 100 banks over the last…

Read more »

Investing Articles

£5,000 invested in these 3 UK stocks at the start of 2025 is now worth…

Mark Hartley breaks down the growth of three UK stocks that helped drive the FTSE 100 to new highs this…

Read more »