1. Not Claiming the Saver's Credit Missing out on a tax credit worth up to $1,000 for individuals ($2,000 for couples) that's specifically designed for lower and moderate-income savers. This is literally free money from the government that can reduce your taxes dollar-for-dollar. 

2. Leaving Money in Cash/Money Market Many people contribute but never actually invest the funds, missing the whole purpose of the Roth IRA. With smaller balances, this lost time is especially costly.

3. Being Too Conservative Too Young Overallocating to bonds or "safe" investments when you have decades until retirement. The opportunity cost is huge when your balance is still building.

4. Missing the Benefits of Professional Portfolio Management Many people don't realize professional advisors often work with accounts under $50,000. A good advisor helps with tax-loss harvesting, rebalancing, and behavioral coaching during market downturns - services that can add 1.5-3% in annual value through improved investment outcomes.

Contribution & Timing Errors
5. Not Prioritizing Roth Contributions Early Missing contribution years when your income is lower (and tax rate is lower). You can't get those early compounding years back.

6. Withdrawing Earnings Before 59½ Not understanding that you can always withdraw your contributions tax and penalty-free after five years, but taking out any earnings before 59½ triggers taxes and penalties. This confusion costs people thousands in unnecessary penalties.

Strategic Mistakes
7. Not Considering Backdoor Roth Conversions Even with a modest balance, missing opportunities to convert traditional IRA or 401(k) money during low-income years.