Since it is not reported on your W-2, any contributions you made are not SEP contributions. You are not permitted to make SEP contributions. Only your employer is permitted to make SEP contributions.
As I suggested as a possibility, perhaps you made a regular personal IRA contribution, not a SEP contribution, but happened to make it to the same SEP-IRA to which your employer makes SEP contributions. If that's the case, it's reported just like any regular personal traditional IRA contribution under Deductions & Credits -> Retirement and Investments -> Traditional and Roth IRA Contributions. These contributions would be reported in box 1 of the Form 5498. The only amounts reported in box 8 of the Form 5498 as SEP contributions are those made by your employer.
