Taxpayer maximum deductible contribution = ~$15k.

Taxpayer AGI = ~$250k.

I get no penalty and no inclusion in income even when I enter SEP contribution of $999,999,999.

This is a 2020 Form 1040, MFJ.  

Spouse has income from W-2, some INT & DIV.

Taxpayer has income from SSA, Schedule C, IRA's [~$115k], and Pensions.

What am I missing?