Add-On Acquisition in Private Equity: Bolt-On vs Platform

An add-on acquisition (also called a bolt-on) is the purchase of a smaller company by a company a private equity fund already owns. The buyer on the purchase agreement is the portfolio company, not the fund. The fund may put in more equity, and the platform's lenders often fund the rest. The point is to fold the target into that platform so the combined business is larger, cheaper to run, or worth a higher multiple than the pieces would have been apart.

Cherry Bekaert's Private Equity Report: 2025 Trends and 2026 Outlook (25 February 2026), using PitchBook, puts add-ons at 72.9 percent of all U.S. buyouts in 2025 by count, in line with the five-year average. They are not most of the dollars. McKinsey's Global Private Markets Report 2025 puts non-platform deals at 40 percent of buyout deal value in 2024. The typical add-on is smaller than the typical platform. Some are not small at all. The same Cherry Bekaert report names Qualtrics' $6.8 billion purchase of Press Ganey Associates, backed by Silver Lake, as one of 2025's largest add-ons.

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Platform versus add-on

The first company in a thesis is the platform: large enough to stand alone, with a management team and systems that can absorb another business. Later purchases in the same thesis are add-ons. PitchBook's report methodologies define an add-on as an acquisition by a company that already has private equity backing. That is a statement about who signs, not about strategy.

People use bolt-on, add-on, and tuck-in for the same purchase. Bolt-on usually means a close operational fit that can be absorbed quickly (same customers, same shops, same back office). Tuck-in usually means smaller still: folded into an existing unit, brand and systems retired. None of those labels is a legal form. If the credit agreement, the purchase agreement, and the integration plan do not match, the nickname does not save the deal.

A buy-and-build is the strategy that uses these purchases on purpose. Bain & Company, in Building a Stronger Buy-and-Build (11 March 2024), counts a buy-and-build as a platform that makes at least four sequential add-ons. About half of add-on deals, in that report, were at least the fourth acquisition by the same platform, up from 21 percent in 2003. A single follow-on still counts as an add-on. Bain starts counting a buy-and-build at four sequential purchases. Add-ons sit inside a buyout, which is one of the types of private equity, not a sixth fund strategy of its own.

Platforms usually command higher multiples because the buyer is paying for scale, reporting, and a team that can do the next deal. Add-ons are often founder-owned, thinner on systems, and sold by a boutique or without a banker. That is why the same earnings can clear at 6x on a shop and 10x on a platform. It is also why a founder being told "you are an add-on" is being told about price and role after close, not about whether the business is any good.

Why add-ons dominate the count

A new platform is a leveraged buyout (LBO): new credit documents, a full quality-of-earnings report, an investment-committee memo built from scratch. An add-on rides the platform that already exists. The check is smaller. Diligence is shorter. The company already has a CFO, a lender, and a board calendar. In a market where large new buyouts are expensive to finance, funds put capital to work by growing what they own.

McKinsey, in How private equity funds can use M&A to create outsize returns, puts add-ons at 70 percent of private equity deal count in 2023, up from 57 percent in 2017. Paul Gompers, Steven Kaplan, and Vladimir Mukharlyamov, in What Do Private Equity Firms Say They Do? (2016), found follow-on acquisitions in more than 50 percent of deals at 79 firms. Follow-on acquisitions are old. What is new is how large a share of deal count they now represent.

Fragmented service businesses (HVAC, dental, field services, parts of professional services) print a lot of these deals because there are many owner-operated companies and few national winners. That is a market structure, not a recommendation to buy any of them.

Multiple arbitrage

Multiple arbitrage is the gap between the multiple paid for the add-on and the multiple the combined company is assumed to be worth. It is an assumption about what the next buyer will pay, not cash in the bank on closing day.

Take a regional HVAC company the fund already owns. It earns $20 million of earnings before interest, tax, depreciation and amortization (EBITDA). The last buyer paid 10.0x, so the platform sits at $200 million of enterprise value. It buys a $3 million-EBITDA shop in the next state. TagniFi's PowerComps, reported by Private Equity Professional (27 August 2026), put the median private equity add-on multiple for businesses with $2 million to $5 million of EBITDA at 6.5x in the second quarter of 2026, against 6.0x for corporate buyers. At 6.5x the shop costs $19.5 million.

If a later buyer still pays 10.0x for the combined $23 million of EBITDA, that business is worth $230 million. The two purchase prices sum to $219.5 million. The $10.5 million gap is multiple arbitrage. It exists only if the market actually applies the platform multiple to the shop's earnings, and only if those earnings survive the combination.

	Platform	Add-on	Combined (no cost cut)
EBITDA	$20,000,000	$3,000,000	$23,000,000
Multiple paid	10.0x	6.5x
Enterprise value paid	$200,000,000	$19,500,000	$219,500,000
If the exit multiple is still 10.0x			$230,000,000

If the platform then cuts $0.5 million of overlapping dispatch and accounting, combined EBITDA is $23.5 million and 10.0x is $235 million. That extra $5 million is operations, not the multiple. If the shop went to auction and cleared 9.0x, the paper gap before any cost cut shrinks to $3 million.

The same TagniFi update shows why the gap exists at all. Businesses with $10 million to $25 million of total enterprise value cleared a median 5.7x adjusted EBITDA. The $25 million to $50 million band was 7.6x. The $50 million to $200 million band was 9.4x. Size still prices. What changed is the old line that a strategic buyer always pays more. On that $2 million to $5 million EBITDA add-on band in the second quarter of 2026, sponsors paid more than corporates.

Bain's 44 buy-and-build deals from 2010 through 2019 is the caution. Platforms that only bought cheaper companies and hoped to sell the pile at a higher multiple averaged a 1.4x multiple on invested capital (MOIC). Platforms that also grew the existing business or improved margins averaged 2.2x. The spread is the strategy, not the nickname.

How the purchase is paid for

The add-on is not a second LBO of the small company. The platform already has a credit agreement. Most follow-ons are funded by some mix of cash the platform has generated, a delayed-draw or incremental term loan on those documents, and follow-on equity from the fund if the facility will not stretch. Mezzanine or preferred equity shows up when the senior line is full.

That is why an add-on can close faster than a new platform. The lenders already know the borrower. It is also why a roll-up that assumed acquisition capacity the credit agreement does not permit dies in the funds-flow. The model has to use the facility that actually exists: accordion, delayed-draw, leverage covenant, and whether add-backs the lender will not accept were used to "create" room.

Internal rate of return (IRR) still cares about timing. A shop bought in year four of a five-year hold has one year to earn the multiple you underwrote. McKinsey's M&A note is blunt on this point: do the add-ons in the first three years of the hold, while there is time to integrate.

Diligence and close

The work looks like any buy-side process, compressed. A teaser or a founder conversation. A defined search (geography, size, customer type), not "a manufacturing company in California." Montage Partners, in What Does an Add-on Acquisition Entail?, notes that smaller transactions often skip a third-party quality-of-earnings review. Skipping the accountant does not skip the questions. Customer concentration, add-backs that are the owner's personal expenses, a key person who will leave, and whether the shop's earnings are real on the platform's chart of accounts still kill deals.

Sourcing is a mix of bankers who already cover the sector, a map the associate keeps, and direct calls to owners who are not in a process. Auctioned add-ons are how the 6.5x median becomes 9x and the arbitrage disappears. Names reached before a process are slower to find and usually cheaper to buy.

Closing is still a purchase agreement, a funds flow, and (often) an earnout. TagniFi put earnouts at 16.5 percent of enterprise value in the lower middle market, with a median life of 24 months. The earnout is how buyers bridge a price the founder will not cut. It is also how integration fights become lawsuits if the metric is not one the combined company can actually produce.

Integration

The thesis on the investment-committee memo is a combined company. The risk is two companies that share a shareholder. CohnReznick, in How top PE firms are winning with add-on acquisitions, calls time-to-integration a key performance indicator and says leading firms get key systems onto one stack within six months of close. The usual failures are ordinary: no owner of the 100-day plan, synergies that never had a name and a date, a founder who will not take the new reporting, customers who leave in the handoff, and three general ledgers at month twelve.

The integration plan is written before signing. Day one is payroll, benefits, and who the customer calls. The first hundred days are the baseline, the chart of accounts, and the cost lines the committee actually believed. Years one and two are whether dispatch, pricing, and procurement are one system. Value creation is that hold-period work.

A buyer at exit will pay a platform multiple for a file they can underwrite: one set of numbers, one management team, documented cost-out, and a map of what is still unintegrated. Uncombined brands do not underwrite that way.

Who does the work

The associate builds the target list, the comparison, and the model that shows the add-on on top of the live platform case. They do not decide whether to buy.

The vice president runs the process: which advisor to hire, which workstream to kill, the short committee note (often shorter than a new-platform memo), and whether the credit agreement actually funds the close.

The portfolio-company chief executive, or a dedicated head of M&A at a busy platform, owns the integration. An operating partner sits on the messy ones. At a middle-market shop the same two investors may do all of that. At a megafund the platform has its own corporate-development person and the deal team only screens. Ask who runs the first Monday after close. That answer is the job.

Common questions

What is an add-on acquisition in private equity?

The purchase of a smaller company by a business a private equity fund already owns. The portfolio company is the buyer. The fund may contribute more equity.

What is the difference between an add-on and a bolt-on?

Most people use the words interchangeably. Some use bolt-on for a target that slots into current operations and add-on for a purchase that adds a new vertical or geography. The documents, not the nickname, decide how it is run.

What is the difference between a platform and an add-on?

The platform is the first, larger company in a thesis. An add-on is bought later and folded in. Platforms usually clear higher multiples. Add-ons are usually smaller and cheaper per turn of earnings.

What is multiple arbitrage?

Paying a lower earnings multiple for the add-on than you think the combined company will be worth. It is not cash until a later buyer actually pays that higher multiple for earnings that survived the combination.

Who pays for an add-on?

Usually the platform: cash, delayed-draw or incremental debt on its existing credit agreement, and sometimes follow-on equity from the fund. It is not a new leveraged buyout of the small company.

Are most private equity deals add-ons?

By count, yes. Cherry Bekaert, using PitchBook, puts add-ons at 72.9 percent of U.S. buyouts in 2025. By dollars they are a minority of buyout value, because the typical add-on is smaller than the typical platform.