Look-through is the process of decomposing a fund holding into its underlying positions and treating them as if they were held directly. The PM's 5% allocation to an external high-yield fund becomes 0.3% in issuer A, 0.2% in issuer B, and so on down the line. The exposure picture changes. Concentration limits that looked comfortable at the fund level might breach at the issuer level once the underlying positions are included.
None of this is new - regulators have required lookthrough functionality for UCITS funds for a while now. The principle that one cannot hide exposure risk behind a fund wrapper is simple, but the implementation is not; so much so that PM's forego owning funds in their portfolios for the sake of compliance.
The first problem is data. Getting the underlying holdings of an external fund requires the fund manager to provide them; sometimes monthly sometimes quarterly - almost never more frequently. Some provide partial data. Some funds provide nothing at all. The PM's ability to do look-through depends entirely on what the external manager is willing (and/or able) to share, and the willingness varies by manager, jurisdiction, firm and relationship.
The second problem is timeliness. Even when the data is available, most of the time it's stale. A quarterly holdings report from an external fund reflects positions that are 30 to 90 days old. The PM is running look-through compliance against a snapshot that may no longer represent the fund's actual holdings, prices, Mv% -- making any attempt at a compliance run feel like an estimate rather than a real check.
The third problem is hierarchy. Look-through requires mapping the underlying positions to the same issuer hierarchy used for the rest of the portfolio. If the PM's system uses a parent-level issuer mapping and the external fund reports at the subsidiary level, someone has to reconcile. If the external fund uses different identifiers (CUSIP vs ISIN, different LEI mappings), someone has to match. This is operational work that scales linearly with the number of external funds in the portfolio.
Most platforms support look-through in the sense that they can ingest a holdings file and decompose a fund position. Fewer support it in the sense that they can automate the data sourcing, handle stale data flags, reconcile identifier mismatches, and run compliance against the combined view in real time. The gap between "we support look-through" and "look-through works without manual intervention" is where most of the operational pain sits.
Credit portfolios with fund-of-funds structures, or mandates that use ETFs for tactical allocation, feel this most. The indirect exposure through fund wrappers is either invisible, stale, or approximate.