there are many different rules. so tell us which category applies, that will simplify our explanation or you can look them up in iRS PUB 590-B starting on page 9
IRA Beneficiaries
The rules for determining required minimum distributions
for beneficiaries depend on whether:
• The beneficiary is the surviving spouse.
• The beneficiary is an eligible designated beneficiary
(defined later) other than the surviving spouse.
• The beneficiary is an individual (other than an eligible
designated beneficiary).
• The beneficiary isn't an individual (for example, the
beneficiary is the owner's estate). (But see Trust as
beneficiary, later, for a discussion about treating trust
beneficiaries as designated beneficiaries.)
• The IRA owner died before the required beginning
date, or died on or after the required beginning date.
https://www.irs.gov/pub/irs-pdf/p590b.pdf
