Holders of tax-deferred retirement accounts are eventually required to withdraw a minimum amount each year whether they need the money or not. The requirement follows directly from how the deferral was granted.
The deferral was always temporary
A traditional retirement account excludes contributions from income in the year they are made and shelters growth from annual taxation.
That treatment postpones a tax liability rather than eliminating it. The government's claim on the balance remains and simply has no due date attached to it.
Without a rule forcing withdrawals, a holder with other income could leave the account untouched indefinitely and pass the deferral to heirs.
The amount is set by balance and life expectancy
The required withdrawal is calculated by dividing the account balance at the end of the prior year by a life expectancy factor from a published table.
Because the factor shrinks with age, the required proportion of the balance rises each year even if the balance itself is falling.
The calculation applies per account type, with rules on whether multiple accounts can be aggregated differing between employer plans and individual accounts.
The withdrawal is taxed as ordinary income
Distributions enter taxable income in the year received, which can push the holder into a higher bracket than their other income alone would produce.
Knock-on effects follow, since income-tested elements of the tax and benefits system respond to the higher figure rather than to spending.
This is why the interaction between required withdrawals and other retirement income is a planning question rather than a purely administrative one.
Failing to withdraw carries a penalty
An amount not withdrawn by the deadline is subject to a penalty on the shortfall, in addition to the tax that would have been due anyway.
Relief is available where the failure was reasonable and steps are taken to correct it, but it requires action rather than being automatic.
Custodians typically calculate and notify the required amount, though responsibility for taking it rests with the account holder.
Roth treatment and charitable transfers change the picture
Roth accounts held by the original owner are generally outside the requirement, because the tax was already paid at contribution.
Rules also permit direct transfers from certain retirement accounts to qualifying charities, which can satisfy the requirement without the amount entering taxable income.
Starting ages, penalty rates and eligibility have been changed by legislation several times, so current published rules and professional advice govern any specific situation.