Your contributions to your SEP plan (that is not a SARSEP) are not reduced by the contributions you or your employer make to your employer’s SIMPLE IRA plan.
SEP plans (that are not SARSEPs) only allow employer contributions. For a self-employed individual, contributions are limited to 25% of your net earnings from self-employment (not including contributions for yourself), up to $49,000. You can calculate your plan contributions using the tables and worksheets.
If your business sponsors another defined contribution plan in addition to your SEP plan (for example, a profit-sharing plan or a 401(k) plan), then your contributions for yourself to all these plans may not exceed 25% of your net earnings from self-employment (not including contributions for yourself), up to $49,000. Note that salary deferrals are not subject to the 25% limit and catch-up contributions are not subject to the $49,000 limit.