People work comes in waves. A layoff, a merger or a sudden departure needs full-time HR leadership for a few months. The rest of the time, a growing company needs steady attention: pay bands, reviews, policies and hiring. That pattern maps onto the two models. Interim CHROs handle the waves. Fractional CHROs handle the steady work.
When an interim CHRO fits
An interim fits when the people workload spikes and has a deadline. Common cases: a reduction in force that has to be planned, communicated and documented correctly; a merger where two workforces need common pay, titles and policies; the departure of a head of people in a company of 200 or more with an HR team that needs a leader; or a serious investigation that occupies senior attention for weeks. Interims typically work full-time for three to six months and are priced around $15,000 to $28,000 a month.
In the US, a layoff at a company of 100 or more employees may trigger the federal WARN Act’s 60-day notice rule, and several states have their own versions with lower thresholds. That alone is a reason to have senior HR leadership in place before announcing anything.
When a fractional CHRO fits
A fractional fits a company of 25 to 150 employees that needs senior people judgment but not a full week of it. The work is building the function: compliance, a handbook, salary bands, a review cycle, a hiring process and manager training. Fractional CHROs usually work 4 to 10 days a month, and quotes typically run $3,000 to $10,000 a month. Engagements often run a year or more, because performance and pay cycles are annual.
Comparing cost
Four months of an interim at $20,000 a month costs $80,000. A year of a fractional at $6,000 costs $72,000. The interim buys concentrated attention for a crisis; the fractional buys a function that works for the year.
The private equity case
After a buyout, people work is heavier than most founders expect. The fund may want a management incentive plan, new employment agreements for leaders, harmonized benefits after add-on acquisitions and a review of pay against the market. An interim CHRO often handles the first wave in larger portfolio companies. Smaller ones, under about 150 employees, usually use a fractional CHRO for the hold period, sometimes the same person across several portfolio companies.
The exit case
Buyers look for people liabilities in diligence: worker misclassification, unpaid overtime exposure, open complaints and claims, missing I-9 forms in the US, inconsistent pay for similar roles, and key employees with no retention arrangement. A fractional CHRO brought in 18 to 24 months before a sale can find and fix those issues while the fix is still cheap. Retention plans for key staff, often a bonus paid on completion of the sale, are also easier to design calmly. An interim during the sale can manage communications and retention, but cannot undo two years of misclassified contractors.
Using both
Some companies keep a fractional CHRO for the steady work and bring in an interim, or extra fractional days, for a single heavy event such as a layoff. If your fractional has handled reductions in force before, extending their hours for a month is often the simpler path.