Negotiate your salary
You may think that if you can't save money, your problem is overspending. But that's not always the case. Sometimes the problem is that your income simply isn't enough to cover the bills and save enough for retirement.
By age 40, you've hopefully developed skills that make you valuable in the workplace. If you've been at your job for a long time, research your salary using sites such as Glassdoor and Payscale, along with U.S. Bureau of Labor Statistics data, to make sure you're being paid competitively. If your salary is on the low end, it may be time to make the case that you deserve a raise based on your accomplishments -- or to start searching for a new, better-paying position. If you're self-employed, it may be time to reassess your hourly or contract rates.
If you don't think that getting a pay raise or switching to a higher-paying job is feasible, then consider whether earning side income is a possibility. Collecting an extra $100 a week of income after taxes and investing that money could add nearly $300,000 to your savings over 20 years, assuming 10% annual investment returns.