Ask in advance if an ETF will generate a standard 1099 tax form or the more complex K-1.

WSJ: BlackRock Wants Some ETFs to Be Sold Under a Different Label

Instead of getting a simple 1099 dividend form, MLP investors receive a more complex K-1 filing with varying degrees of tax deferral and sometimes even taxable income in multiple states.

FORBES: Magazine Article

However, 401(k) problems are complex and multi-layered.

FORBES: The Shape of Things to Come (December 1, 2001)

Under the current system, all companies with 401(k) plans must pass complex "nondiscrimination" tests annually.

FORBES: Taxing Matters: Saving to the max

Our experience would confirm this. 401(k) record-keeping is exceedingly complex.

FORBES: 401(k)s: Far More Dangerous Than IRAs (March 2, 2001)

As background, the 401(k) rules from the DOL and IRS are complex.

FORBES: 5 Characteristics of a Great 401(k) Plan

The partnership information (Form K-1) which tends to run twenty pages or more is fiendishly complex.

FORBES: Tax Preparer Viewpoint

Lawmakers from the U.K., France and Australia are trying to squeeze more tax revenue from such companies amid concerns that complex corporate structures are depriving their countries of taxes they believe are due.

WSJ: Apple Pays No Tax on Much of Its Overseas Income, Senate Panel Finds