I assume that you are a sole proprietor or a partner in a partnership, otherwise the SEP contribution is reported on the business's tax return. A SEP contribution is entered in the self-employed retirement section of the business section of TurboTax. It is not to be entered anywhere under Deductions & Credits.
For a sole proprietor or partner, the limit for a SEP contribution is 20% of net earnings, not 25%. Net earnings are net profit from self-employment minus the deductible portion of self-employment taxes.
