Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

Is it a good idea to rebalance without withdrawing money?
Rebalancing has been studied empirically quite a bit, but not particularly carefully and actually turns out to be very hard to study well.  The main problem is that you don't know until afterward if your target weights were optimal so a bad rebalancing program might give better performance if it strayed closer to optimal weights even if it didn't do an efficient job of keeping near the target weights. In your particular case either method might be preferred depending on a number of things: You can see why there isn't a generally correct answer to your question and the results of empirical studies might very wildly depending on the mix of assets and risk tolerance.  Still if your portfolio is not too complicated you can estimate the costs of the two methods without too much trouble and figure out if it is worthwhile to you. EDIT In Response to Comment Below: Your example gets at what makes rebalancing so hard empirically but also generally pretty easy in practice.  If you were to target 75% Equity (25% bonds?) and look at returns only for 30 years the "best" rebalancing method would be to never rebalance and just let 75% equity go to near 100% as equity has better long term returns.  This happens when you look only at returns as the final number and don't take into account the change in risk in your portfolio. In practice, most people that are still adding (or subtracting in retirement) to a retirement portfolio are adding (removing) a significant amount compared to the total amount in their portfolio.  In the case you discribe, it is cheaper (massively cheaper in the presence of load fees) just to use new capital to trade toward your target, keeping your risk profile.  New money should be large enough to keep you near enough your target.  If you just estimate the trading costs/fees in both cases I think you'll see just how large the difference is between the two methods this will dwarf any small differences in return over the long run even if you can't trade back all the way to your target.