Decide Whether to Rebalance a Portfolio That Has Drifted From Target

The target was 80/20 and the market has quietly turned it into 88/12, which is not the risk you signed up for. This weighs the dealing and tax cost of rebalancing now against leaving it to new contributions, and gives you a clear drift threshold worth acting on.

Decide whether to rebalance a portfolio that has drifted from its target allocation of {TARGET_ALLOCATION} to its current allocation of [current allocation, e.g. 75/25]. Weigh the cost of rebalancing, including dealing charges and capital gains tax if selling outside a tax wrapper, against the risk of leaving the portfolio more concentrated than intended, and state a clear threshold, a percentage drift, at which rebalancing becomes worth doing rather than being left to new contributions to correct gradually.