That indicates that you rolled over a before tax 401(k) plan to an after-tax Roth IRA. You must pay the tax on the box 2a amount of the roller. Only a rollover to a Traditional IRA would be tax free since both the 401(k) and Traditional IRA are before tax accounts.
Conversions from a before tax account to an after-tax account is always taxable unless you had after-tax contributions in the account, but a blank box 5 indicates you had none.
You were mistaken if you thought that it would not be taxable.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
