What is "IRS Distribution Code" for 401K withdrawal?

It is a code used to designate the nature of the 401K withdrawal.

It is found on the Form 1099-R and tells the IRS how the distribution should be taxed.

It depends on what kind of distribution it was. Here is the list:

Distribution Code Meaning
1 Early distribution, no known exception
2 Early distribution, exception applies
3 Disability
4 Death
5 Prohibited transaction
6 Section 1035 exchange
7 Normal distribution
8 Excess contribution
9 Cost of life insurance protection
A May be eligible for 10-year tax option
D Excess contribution
E Excess annual additions
F Charitable gift annuity
G Direct rollover
J Early distribution from Roth IRA
L Loans treated as deemed distributions
N Recharacterized IRA contribution
P Excess contribution
Q Qualified distribution from a Roth IRA
R Recharacterized IRA contribution
S Early distribution from a SIMPLE IRA in the first two years, no known exception
T Roth IRA distribution, exception applies