A fund closes, deploys capital, returns distributions, and posts a strong IRR. The headline number looks clean. What it may not reflect is that the clock on that IRR started later than you think, because a subscription credit facility was sitting between the LP capital call and the actual investment for anywhere from sixty to one hundred eighty days.

How Subscription Lines Actually Work

A subscription credit facility is a short-term revolving credit line extended to a fund, secured not against portfolio assets but against LP capital commitments. The lender, typically a large commercial bank, underwrites the creditworthiness of the LP base rather than the underlying investments. When a deal closes, the fund draws on the line instead of calling LP capital immediately. The LP call comes later, often weeks or months afterward, and repays the facility.

The mechanics are straightforward and the operational rationale is real. Sub lines reduce the friction of capital calls, letting GPs move quickly on time-sensitive transactions without waiting for wire transfers from dozens of LPs. For LPs, fewer capital calls means lower administrative burden. There is legitimate utility here. The structural distortion is a separate matter.

The IRR Inflation Mechanism

IRR is acutely sensitive to the timing of cash flows. Delay the LP’s initial capital outflow by ninety days, and the annualized return rate on that capital improves materially, even if the underlying asset performance is identical. A fund that uses a sub line aggressively through its early deployment period can post an IRR in years one through three that bears little relationship to realized asset returns.

• The clock manipulation: IRR calculation begins at the LP capital call, not at fund close or asset acquisition. A sub line pushes that call date forward.
• The compounding effect: Early vintage IRRs, when deals are being seeded and sub lines are most active, carry disproportionate weight in the final fund IRR calculation.
• The benchmark problem: Peer comparisons and quartile rankings use IRR as a primary metric. Funds that use sub lines more aggressively appear stronger on that metric without necessarily generating stronger returns.

Academic work, including research published by the Journal of Finance and independent LP advisory firms, has estimated that aggressive sub line usage can inflate reported IRRs by two to six percentage points on an annualized basis in early fund years. The effect moderates as the fund matures and lines are repaid, but the reputational and fundraising benefit to the GP has already been captured.

What Sophisticated LPs Compare Instead

Institutional allocators who have worked through this are increasingly asking for IRR figures calculated from the date of investment, not the date of capital call. Some request both metrics side by side. Others are placing greater analytical weight on total value to paid-in capital (TVPI) and distributions to paid-in capital (DPI), which are indifferent to timing manipulation and reflect actual cash movement.

DPI in particular is gaining attention. A fund with a high IRR but low DPI in a mature vintage is a structural signal worth examining. It may indicate that sub line usage extended apparent performance, that exits are being delayed, or both. The combination deserves scrutiny before a re-up decision.

The Operator Read

Sub lines are a legitimate treasury tool that became, in some hands, a quiet marketing instrument. The structural setup now favors LPs who ask for investment-date IRR alongside call-date IRR, who treat TVPI and DPI as primary filters, and who understand that a manager posting strong early IRRs in a rising rate environment, where sub line borrowing costs are no longer trivial, is carrying a different cost structure than their 2018 vintage peers. The number on the page is always a starting point. The methodology behind it is the conversation worth having.