Peter Stephens | Friday, 1st January, 2021 Our 6 ‘Best Buys Now’ Shares “This Stock Could Be Like Buying Amazon in 1997” Enter Your Email Address Making a passive income that doubles the State Pension may sound like an unrealistic goal to many investors. However, investing money in a range of high-quality UK shares could produce impressive results over the long run.With many FTSE 100 companies currently trading on low valuations even after the stock market rally, now could be the right time to start building a portfolio. Over time, a modest monthly investment could provide greater financial freedom in retirement.5G is here – and shares of this ‘sleeping giant’ could be a great way for you to potentially profit!According to one leading industry firm, the 5G boom could create a global industry worth US$12.3 TRILLION out of thin air…And if you click here we’ll show you something that could be key to unlocking 5G’s full potential…Investing in UK shares to double the State PensionIn the past, saving money on a regular basis provided an opportunity to build a passive income that boosted the State Pension. For example, an individual may have saved £100 per month over their lifetime. At retirement, this could have provided a decent income while interest rates were at historically ‘normal’ levels of 4%+.Similarly, bonds were an attractive option for those seeking to build an income for retirement. However, interest rates are now at extremely low levels. So that means neither cash nor bonds are likely to provide sufficient returns in the coming years. Certainly not enough to build a passive income that increases financial freedom in retirement.As such, investing in UK shares is a more realistic means of generating a passive income in older age that boosts the State Pension. Certainly, shares are riskier than cash or bonds in the short run. However, investing in them over the long run has historically been a sound means to build a portfolio from which an income can be drawn in older age.Investing money on a regular basis to make a passive incomeHistorically, investing money in UK shares to make a passive income that boosts the State Pension was too costly for many people to consider. However, today, the cost of buying and selling shares is extremely low due in part to online share dealing. As such, it’s possible to invest £100 per month to produce a portfolio that delivers a generous income return in older age.In fact, a £100 monthly investment could even double the income many people receive in retirement. The FTSE 100 has produced annual total returns of 8% in its 36-year history. Assuming the same returns in future would turn a £100 monthly investment into a sum of £230,000 within 35 years. From this, a 4% annual withdrawal amounts to £9,200. That’s a similar amount to the State Pension.Taking a long-term viewTherefore, using UK shares to build a passive income could be a sound means of supplementing the State Pension. Through taking a long-term view, an investor can overcome the short-term volatility inherent in the FTSE 100’s performance.Over time, it could deliver significantly higher returns than those available from other passive income strategies, such as holding cash or bonds. Simply click below to discover how you can take advantage of this. Click here to claim your copy now — and we’ll tell you the name of this Top US Share… free of charge! I would like to receive emails from you about product information and offers from The Fool and its business partners. Each of these emails will provide a link to unsubscribe from future emails. More information about how The Fool collects, stores, and handles personal data is available in its Privacy Statement. See all posts by Peter Stephens I’m sure you’ll agree that’s quite the statement from Motley Fool Co-Founder Tom Gardner.But since our US analyst team first recommended shares in this unique tech stock back in 2016, the value has soared.What’s more, we firmly believe there’s still plenty of upside in its future. In fact, even throughout the current coronavirus crisis, its performance has been beating Wall St expectations.And right now, we’re giving you a chance to discover exactly what has got our analysts all fired up about this niche industry phenomenon, in our FREE special report, A Top US Share From The Motley Fool. Image source: Getty Images 3 passive income ideas I’d use to double the State Pension with £100 per month Renowned stock-picker Mark Rogers and his analyst team at The Motley Fool UK have named 6 shares that they believe UK investors should consider buying NOW.So if you’re looking for more stock ideas to try and best position your portfolio today, then it might be a good day for you. Because we’re offering a full 33% off your first year of membership to our flagship share-tipping service, backed by our ‘no quibbles’ 30-day subscription fee refund guarantee.