The Revolver as an LBO Cash Plug, Explained

Answer:
The sequence that spawns the circularity:

1. FCF is computed (which includes interest on all debt).
2. Mandatory amortization is paid.
3. Cash is brought to the minimum, if cash is below minimum, a revolver draw is needed.
4. The revolver draw incurs interest expense, which reduces FCF, potentially increasing the required draw.
5. If excess cash exists after the sweep, the revolver is paid down, which lowers interest, increases FCF, and increases the sweep, a loop in both directions.
   The circular reference interlinks revolver balance ↔ revolver interest ↔ FCF ↔ sweep/required draw.

To break it without iterative calculation, base the revolver draw on the cash shortfall before considering the incremental interest from the revolver itself (i.e., using the beginning revolver balance of zero for interest). After the draw is determined, one can recalculate interest on the average revolver balance as a separate, non-iterative step or simply accept the inaccuracy.

The approximation error is that interest on the drawn revolver is not fully reflected in the FCF that sized the draw, leading to an understatement of the true draw needed when the revolver is heavily used. This error grows material when the revolver draw is large relative to total interest or when the interest rate on the revolver is high.

Follow-up pressure:

1. "If you use the iterative calculation method instead, what Excel settings would you adjust, and what is the risk of a 'circular reference' warning if the model is not built carefully?"
2. "How does the revolver commitment fee on the undrawn portion further complicate the circularity? Should the fee be based on the average undrawn amount or the beginning-of-period amount?"
3. "In a downside scenario where the revolver is heavily drawn, the model might show the revolver balance increasing each year. What does that indicate about the sustainability of the capital structure, and how would lenders react?"