Interim, fractional and full-time are three different purchases.

The enquiry usually arrives in the same shape. Somebody has left, or has given notice, or the business has reached a point where a number cannot be explained by anybody currently in the building. The question asked out loud is what it costs to bring somebody in. The question underneath it is which kind of somebody, and that is the one that decides whether the money is well spent.

Interim and fractional are used as though they describe the same arrangement at different intensities. They do not. They answer different questions, they are priced on different bases, and they fail in different ways.

An interim is cover

There is a seat. It existed before, it has just emptied, and the business cannot afford for it to stay empty. Payroll has to run, the lender has to be answered, the year end has to be signed. An interim steps into that seat, usually four or five days a week, usually for somewhere between three months and a year, and the job is defined by the shape of the gap rather than by any view about what the business ought to become.

Because the model rests on presence, it is priced on presence. A senior day rate across a near-full week costs close to what the permanent salary would have cost, and frequently more once the recruitment fee for the eventual replacement is counted. That is not an argument against it. If nobody left in the business knows how to close the month, presence is exactly the right thing to buy, and buying it late costs more than buying it dear.

What a fractional CFO is filling instead

Here there is no seat. There has never been a seat, because the business has never been able to carry one, and the work a CFO would have done has been absorbed by whoever had capacity, which in most owner-led businesses means the person who owns the place. Nothing has emptied. Something has simply never been filled.

The job is therefore defined by the decision calendar rather than by the working week. Two or three days a month can be sufficient, because what is being bought is judgement on the small number of matters that move money, together with ownership of the function that produces the information those decisions rest on. The comparison is not against a salary. It is against the cost of the decisions the business is currently making without that input, which is real money and appears on no invoice.

And what a full-time CFO is for

There is a third answer, and it is not the fractional one with more days on it.

A full-time CFO makes sense when running the function has become the job in its own right: a team to manage day to day, several entities with daily operations, and obligations arriving faster than anybody can batch them. That is a question about the size of the function, not the size of the business and not the size of the budget.

Two conditions travel with it. The strategy has to be stable enough to plan twelve to twenty-four months against, because you are hiring for a direction rather than for a moment. And a proper search runs two to four months before anybody starts working a notice period, which means a full-time CFO cannot answer a problem you have this quarter. If the answer is a full-time CFO, the work starts now.

Two of the three are one line

Set out against the growth of the business rather than against a calendar, fractional and full-time stop looking like two products. They are the same line at different points on it. Fractional has no end date in it: it starts at half a day a week, it deepens as the business does, and it ends by becoming the seat above it, at a point the business arrives at rather than a date anybody agreed in advance.

The three ways of getting it wrong

Appointing an interim when the problem was structural produces twelve steady months and a business that returns to precisely where it started on the last day. Everything ran. Nothing changed. The information is no better than it was, and the next vacancy will feel exactly like the last one.

Appointing a fractional CFO when the problem was cover produces the opposite failure. The design work is sound, the reporting improves, and then something breaks on a Tuesday and there is nobody in the building. Cover is a presence problem, and no quantity of good design substitutes for somebody being there.

Appointing a full-time CFO when the function did not need managing full time produces a senior person with too little to own. They arrive, build the thing that was missing inside six months, and spend the next eighteen looking for work that justifies the seat. That is expensive, and it usually ends with them leaving.

Sometimes the answer is both, in order. A short interim to stabilise, followed by a fractional appointment to rebuild, is a sensible sequence and a common one. The mistake is not using both models. It is buying one of them while describing the problem as the other.

None of the three labels is regulated

Anybody may describe themselves as either. The words carry no qualification, no defined scope, and no accountability of their own, which makes the label the least informative part of any proposal. Three things are worth establishing in writing before anything is signed.

The first is what the person is accountable for, as distinct from what they will advise on. The second is whether they hold any statutory or officer position, because an interim frequently does and a fractional appointment frequently does not, and the business needs to know which and to have the authority recorded either way. The third is what will exist on the last day that did not exist on the first.

A vacancy, a capability, or a job

That is the question that settles it. A vacancy is a seat that used to be occupied and is not. A capability is something the business has never had and has been paying for the absence of, usually without ever seeing the charge. The first is an interim question. The second is not, and no interim appointment will answer it, however good the appointee.

Most owner-led businesses asking the question are in the second category and describe themselves as being in the first, because a vacancy is easier to explain to a board and easier to price. It is also the wrong purchase, and the cost of the error only becomes visible on the day the cover ends.

The third category is different again, and rarer than it sounds. A job is what you have when running the function occupies somebody five days a week on its own merits, rather than because nobody has designed it yet. Businesses reach it later than they expect, and a good many that describe themselves as being in it are in the second.

None of them works without an owner

All three fail in the same way when nobody is accountable for the outcome. A person who attends, reports, and advises is not the same as a person who owns whether the finance function works, and that distinction survives every label the market invents. The useful test is not how many days a week somebody is present. It is what the business can still do on the day they stop.