Are large and frequent moves via rebalancing within a 401k, without cost or penalty?

External question — Personal Finance Stack Exchange Author: Greg McNulty Original post: https://money.stackexchange.com/questions/135746 License: CC BY-SA 4.0 — https://creativecommons.org/licenses/by-sa/4.0/ Adaptation: HTML converted to plain text; contact email addresses removed. Example scenario: 300k vested in companies 401k Company provides 10 funds, from low to high risk Each fund has extensive details, that can be used to relate to current market volatility. Company provides online re-balancing tools from/to any of the 10 funds One week the employee expectes a market crash. He sells/buys via re-balancing all his/her funds and places them into the companies stable fund. The next week, believes a certain sector will do very well and one of the companies funds is heavily mixed in it. Again sells/buys via rebalancing into that fund. Etc, etc. each week or couple of days. In a standard trading account, large weekly moves are penalized with long/short term gains tax, brokerage fess, purchase/sell fees. Are large and frequent moves within a 401k (like the example above) without cost or penalty?