It may depend on the type of employer plan, and the plan's limits. The
most common employer plan is a 401k, and you can hypothetically
contribute 100% of your salary, up to $18,000 (2017 amount) or if you
are over age 50, $24,000 (2017 amount). You should ask your employer about any limits.
You can contribute up to
$5500 to an IRA ($6500 if age 50 or older). However, the deduction may
be limited, depending on your total income.
https://www.irs.gov/retirement-plans/2017-ira-deduction-limits-effect-of-modified-agi-on-deduction-i...Your self employed business can also set up its own retirement plan, such as a SEP or its own 401k plan.
https://www.irs.gov/retirement-plans/retirement-plans-for-self-employed-people
