On the 1040A, where/how do I report a rollover from a 401K Plan to a traditional IRA. I did not receive a 1099-R for this transaction. Only a letter from the 401K provider documenting the rollover.

[KatrinaB]

If you didn't receive a form 1099-R, then you probably did a trustee to trustee transfer of the funds. In this case, you will not need to report anything on your tax return.

[dmertz]

Only trustee-to-trustee transfers from one IRA to another of the same type are not reportable.  Since a 401(k) is involved, the plan is required to report it in Form 1099-R or it's equivalent (a substitute format that qualifies as a Form 1099-R).

[dmertz]

The 401(k) plan must issue a Form 1099-R for this distribution.  If the document provided by the plan is not simply a Form 1099-R provided in a nonstandard format, including the distribution code, contact the 401(k) plan to obtain the missing form.