When it comes to retirement, you don't want to end up with too little. The good news is that you could stop this from happening by investing in ASX shares.

For example, investing just $500 a month into high-quality ASX shares could be the key to building a million-dollar retirement portfolio.

The secret lies in consistency, time, and the power of compound returns. Here's what you need to know:

The power of long-term investing

The Australian share market has historically delivered an average annual return of around 10%, including dividends. By committing to investing $500 every month and reinvesting the returns, you could amass a substantial sum over time if this trend continues.

If you followed this strategy for 30 years, earning a 10% annual return, your portfolio would grow to just over $1 million. This is the magic of compounding—your returns generate more returns, and over time, this snowballs into serious wealth.

Which ASX shares?

The ASX is home to a range of high-quality shares that have stood the test of time. Companies with strong market positions, reliable cash flows, and shareholder-friendly policies (such as regular dividends) tend to perform well over the long run.

When selecting ASX shares for long-term wealth building, it's important to focus on companies with strong fundamentals. Here are a few characteristics to look for:

• Strong competitive advantages – Companies with unique products, pricing power, or dominant market positions tend to outperform.
• Consistent revenue and earnings growth – Businesses that steadily grow their profits are more likely to generate strong returns.
• Reliable dividend payers – Many ASX blue-chip stocks reward shareholders with growing dividend payments, providing an additional stream of income.

Some examples of high-quality ASX shares that have historically performed well include Goodman Group (ASX: GMG), TechnologyOne Ltd (ASX: TNE), ResMed Inc (ASX: RMD), and Wesfarmers Ltd (ASX: WES).

The importance of consistency

The biggest advantage of investing $500 a month is that it removes the need to time the market.

Whether the market is up or down, you continue investing, benefiting from dollar-cost averaging. This strategy allows you to buy more shares when prices are low and fewer when prices are high, smoothing out market volatility.

Foolish takeaway

Investing in ASX shares consistently over a long period can help secure a comfortable retirement.

By sticking to a disciplined approach and allowing compound interest to work its magic, you could be setting yourself up for financial freedom.

If you're patient and committed, $500 a month could be all it takes to retire rich.