Social Security is an important income source for many seniors. But its future is iffy, and that has today's workers worried. In fact, 73% of them are concerned that Social Security won't be there for them once they're set to retire, according to the 21st Annual Transamerica Retirement Survey.

The question is: Are they right?

The real deal with Social Security

Social Security needs revenue to keep up with benefits, and it gets most of its revenue from payroll taxes. That means that as long as we have an active workforce and keep taxing paychecks, the program can continue to operate. Or to put it another way, Social Security is not in danger of going away completely because its main revenue source is still more than viable.

That said, the workforce is expected to dwindle in the coming years. As baby boomers retire in droves and too few workers come in to replace them, Social Security will have a financial shortfall on its hands. That's because it's expected to owe more in benefits than it collects via payroll tax revenue.

Four Social Security cards.

Image source: Getty Images.

What does that mean? In short, it means that benefit cuts could be on the table in the not-so-distant future.

To be clear, Social Security does have trust funds it can tap in the near term to make up for a revenue shortfall. Think of those trust funds as a savings account of sorts that can be raided in a pinch. But once those trust funds run out of money -- which could easily happen within the next 15 years -- the program could start paying seniors less money.

That would, of course, be a bad situation for current retirees who are already heavily reliant on their existing benefits. And it could also hurt future retirees who need Social Security to stay afloat. But if you fall into the latter category and are still a member of the workforce, the silver lining is that you still have a chance to ramp up your savings and compensate for what could be a lower monthly Social Security benefit down the line.

Save while you can

Even if Social Security isn't forced to cut benefits, the income you receive from it will only replace about 40% of your pre-retirement wages, assuming you're an average earner. (If you're an above-average earner, Social Security will provide even less replacement income.) Most seniors need about twice that much money to live comfortably, so either way, your goal should really be to enter retirement with a solid nest egg you've built yourself.

To make that happen, put yourself on a budget so you're able to carve out room for monthly saving. Then, consistently put money into an IRA or 401(k) plan.

But that's not all. It's important to invest your savings so your money grows into a larger sum. In that regard, stocks are your best bet. Stocks carry some risk, but if you have a lengthy savings window ahead of you, they're a solid bet.

You can buy individual stocks for your retirement plan if you have an IRA, though 401(k)s generally don't offer this option. Otherwise, index funds that track major indexes like the S&P 500 are a good bet. That way, you get to invest in the broad market and capitalize on its gains.

If you sock away $400 a month in a retirement plan over the next 30 years, and your investments generate an average annual 7% return during that time (which is a bit below the stock market's average), you'll end up with over $450,000 to your name. Make it $600 a month, and you'll have more like $680,000 to work with. That could make for a comfortable retirement, even with reduced Social Security benefits.

While Social Security is not in danger of drying up, you may not get as robust a benefit as you'd hope for. Save accordingly, and that won't prevent you from enjoying your senior years to the fullest.