TSP and 401(k) contrasts

In-plan Roth conversions
While 401(k) plans with a traditional and Roth option may allow in-plan conversions from traditional to Roth, the TSP does not. As of November 2013, the TSP is studying the idea of permitting in-plan Roth conversions and has listed this as an initiative for further action in 2014.

Partial withdrawals
The TSP allows separated employees to make a single lifetime partial withdrawal, for example to a traditional or Roth IRA. A 401(k) plan, by contrast, may allow more than one partial withdrawal for separated employees.

Incoming rollovers into Plan
The IRS permits employer sponsored retirement to allow participants to roll over certain eligible accounts into the plan, such as IRAs or 401(k)s from previous jobs. While these plans are permitted to offer this option, they are not required to, and many 401(k) plans have different rules on whether a participant is allowed to roll over an account into their 401(k) plan. Additionally, while most plans will allow current employees to roll over assets into the plan, many plans won't allow former employees to do so.

The TSP allows both current and separated employees to roll over traditional pre-tax IRAs and eligible employer plans into their TSP accounts.