immediately, if not sooner.
A problem many asset managers face is that the client asks you to raise the money, but then takes days, weeks, or perhaps even months to wire the funds out, all the time the cash is sitting in the portfolio, but you can't touch it! And, its mere presence is impacting your return. This cash, once raised, is arguably non discretionary, and should be isolated.
GIPS(R) (Global Investment Performance Standards) permits firms to temporarily remove an account from its composite in the event of a large flow, but this only solves part of the problem: the portfolio's return will continue to reflect this cash. And, what if the cash is still present after the allotted removal time has expired?
A better solution is to use a temporary account. The problem is that this can be a challenge for many, especially when you have to reconcile with the custodian.Perhaps a better solution is to identify this cash as "unsupervised." This is an analogous approach. Some systems support this, and you should consider employing this technique, where applicable.