You can only contribute to your SEP up to 25% of your net business income or $55,000, which ever is less.
The 2019 cap is $56,000.
For more information, follow this link:
https://blog.turbotax.intuit.com/self-employed/end-of-year-retirement-tips-for-employees-and-the-sel...
Here is the IRS link confirming the contribution amounts:
https://www.irs.gov/retirement-plans/retirement-plans-faqs-regarding-seps-contributions
[Edit 3/25/2019 11:15 AM PST]
