Second Lien and Unitranche Structures

A company borrowing $300 million doesn't have to structure it as one loan with one interest rate. It can split the borrowing into layers with different claims on collateral if things go wrong, or borrow it as one blended facility that behaves like layers internally without the borrower ever seeing the seams.

Second lien debt is a separate tranche, contractually subordinated to a first lien tranche: both are secured by the same collateral, but the first-lien lender gets paid from that collateral before the second-lien lender sees a cent. A unitranche loan is the newer alternative, common in private credit: a single loan, one interest rate, one set of terms visible to the borrower — but behind the scenes the lenders participating in it have privately agreed to split that single loan into a senior "first-out" slice and a junior "last-out" slice via an agreement among lenders (AAL).

Two ways to slice the same risk

Worked example

A company needs $250 million. Compare two structures.

Second lien: $180 million first lien at 6.5%, $70 million second lien at 10.5%. The borrower manages two agreements, two covenant sets, and two lender groups who must sign an intercreditor agreement governing who controls remedies in a default.

Unitranche: the same $250 million as a single loan at a blended rate. Behind it, lenders privately split it: $180 million "first-out" earning roughly 6.5%, $70 million "last-out" earning roughly 10.5%, with the AAL specifying that first-out lenders get repaid ahead of last-out lenders and typically control default remedies. Blended rate to the borrower:

$$r_{blended} = \frac{180 \times 6.5\% + 70 \times 10.5\%}{250}$$ $$r_{blended} = \frac{1170 + 735}{250} = 7.62\%$$

In words: the single rate the borrower pays is just a size-weighted average of the two internal slices — the borrower experiences one number, one covenant package, and one point of contact, even though the underlying economics are identical to the second-lien deal.

What this means in practice

Unitranche structures grew fastest in the private credit boom because a single direct lender (or a small club) can write the whole check, giving borrowers speed and certainty of execution that a syndicated first-lien/second-lien deal can't match — no separate intercreditor negotiation with an outside second-lien lender, no execution risk from a broadly marketed syndication. The tradeoff shows up only in default: unitranche last-out holders discover exactly how subordinated they are through the private AAL, a document the borrower typically never sees and has no say in.