Stub Periods in Models and Interviews

A stub period is a partial year (or partial month) at the start of a model because the deal closes mid-year or mid-quarter. Interviews care that you do not treat a 3-month stub like a full year of cash flow. The concept shows up in LBOs, DCFs, merger models, and real estate underwriting whenever cash actually moves on a date that is not a clean fiscal year-end.

The short answer

"A stub is the stub year from close to fiscal year end or to the next model calendar break. I scale earnings and cash flows for the fraction of the year remaining, adjust interest and debt balances for the actual days outstanding, and I discount or compound returns using the real timing. I do not annualize blindly."

When stubs appear

If the prompt never gives a close date, ask. Many paper LBOs silently assume year-end close so you can skip the stub. That assumption is fine if you state it. Blindly inventing a stub when the interviewer meant annual columns is how you burn clock.

Modeling instincts

Stub Fraction ≈ Days Remaining in Year / 365
Stub EBITDA ≈ Annual EBITDA × Stub Fraction
(seasonality can break this; say so)

What gets prorated vs what does not

Flow items usually scale: revenue, COGS, operating expenses, taxes on operating income, and maintenance CapEx that tracks the period.

Stock items do not prorate the same way. Opening cash, debt principal, and NWC balances are point-in-time. Interest accrues based on days capital has been outstanding. Transaction fees land at close, not smoothed across the stub unless the docs say otherwise.

Seasonality warning

Retail, restaurants, hotels, and many RE assets make equal-day stubs wrong. If 70% of EBIT comes in Q4 and you close in October, a naive 3/12 scale fails. Mention seasonality when the business earns it. Prefer monthly or quarterly shapes over day-count times annual EBITDA when guidance exists.

Returns and discounting

IRR is sensitive to stub timing. Closing in March versus December changes when equity goes in and when the first cash flows arrive. MoIC can look identical while IRR diverges. Say that clearly if they ask why stubs matter for PE returns.

In DCFs, a stub first period changes both the cash in period 1 and how many years to the terminal. Mid-year conventions are related but not identical: see Mid-Year Convention in DCF. Mid-year is a discounting assumption inside annual periods. A stub is an actual partial operating period after close.

Merger model and EPS stubs

In M&A, a mid-year close means pro forma EPS for the deal year is not a full year of target earnings plus full-year synergies. Phase-in and stubbing interact. If Year 1 includes only six months of the target, your accretion math must match. Clarify calendar year versus first twelve months when you quote accretion.

Common traps

1. Treating stub EBITDA like a mini annual year and annualizing returns off it
2. Charging a full year of interest on debt drawn at close in a 3-month stub
3. Ignoring seasonality in retail or RE
4. Building IRR as if equity funded on Jan 1 when close is mid-year
5. Forgetting transaction fees and cash to close sit at the close date

Interview verbal

"A stub period is a partial first period after close. I prorate operating cash flows, accrue interest for actual days, and keep IRR dates honest. If the business is seasonal, I avoid naive day-count proration. If the prompt is silent on close date, I ask whether to stub or assume year-end close."

Worked intuition

Close June 30, annual EBITDA 100, non-seasonal: stub EBITDA about 50. Debt 400 at 8%: about half-year interest (~16), not 32. Equity funds at June 30, so a 4.5-year hold from close is not "year 4" on a Jan 1 clock.

Related

Mid-Year Convention in DCF and Walk Me Through an LBO. For deal-year M&A timing, pair with Walk Through a Merger Model. Practice dating cash flows on Project Catalyst.