Schedule SB, Single-Employer Defined Benefit Plan Actuarial Information, is the actuary's annual statement of the plan's funding. It records the valuation date, the plan's assets, the funding target and normal cost, the segment rates and mortality table used, the contributions made and the minimum required contribution. The enrolled actuary signs it, stating that prescribed assumptions follow the law and the others are reasonable.
Larger plans attach it to Form 5500. A one-participant plan filing Form 5500-EZ does not. The Form 5500-EZ instructions still require the actuary to complete and sign a Schedule SB each year, and the plan to keep it with its records. The annual valuation is required even in years when assets are under $250,000 and no Form 5500-EZ is due, and a Schedule SB is completed for a plan's first year when the plan is adopted after that year ends.
One figure from it does reach the return: Form 5500-EZ asks for any unpaid minimum required contribution, taken from the Schedule SB. As plan administrator, you keep the signed copy. See the Form 5500-EZ guide.