Why Retirement Income Comparisons MatterTwo individuals can invest the same amount in different contracts, resulting in varied income estimates. Income taxes and required debt payments. A period-certain provision instead guarantees payments for a stated number of years, or combines a lifetime payment with a minimum payment period. Separate Guaranteed Income From Projected GrowthA guaranteed payment is different from a projected account value. The best retirement income option is one that supports essential expenses while preserving enough flexibility for taxes, emergencies, and changing priorities.