Which do you need:an interim, an accountant, a financial manager, or a CFO?

Interim, fractional and full-time are not three sizes of the same thing, and the labels are the least informative part of any proposal. What follows sets out how the three actually differ, on the two dimensions that decide between them, and then puts six questions to you that end in one of seven answers. Two of the seven are not a hire at all.

Fractional and full-time are one line. Interim is not on it.

Fractional does not run for a period and then stop. It starts at half a day a week, grows as the business does, and ends by becoming the seat above it. So the axis that matters is not how long the arrangement lasts. It is how big the business has become, and how much of the week the function needs somebody as a result.

Scroll the chart sideways.

What the finance function needs as the business grows A rising line shows how many days a week the finance function needs somebody, plotted against the growth of the business. Below half a day a week the founder is still doing it. From half a day to three days a week is fractional territory. Four to five days is full-time territory. The line crosses from one into the other at a handover point set by the business rather than by a contract. An interim does not appear on this line, because it is triggered by a seat emptying rather than by growth. 012 345 Days a week the function needs Early. One entity, one market, a handful of people. Larger. A team, several entities, obligations arriving daily. The business grows Full-time Five days, no end date. Running the function is the job. The handover Not a date. A point the business arrives at. Fractional Half a day at the start, three days later on. No end date on it either. It ends by crossing the line above, when the function needs somebody every day. Below half a day a week, the founder is still doing it.
Fractional and full-time are the same line at different points on it, which is why moving from one to the other is a handover rather than a replacement. Nothing on this chart says when the arrangement ends, because the business decides that and not the contract.
Interim does not appear on this chart. An interim is not a point on the line, because it has nothing to do with how big the business is. A seat empties, and it is filled at four or five days a week at whatever size the business happens to be, for three to twelve months. It is the only one of the three with an end date built into it, and that date is set by the permanent search running alongside it.

The dimension that decides it in practice.

Whichever is right in principle, only one of the three can answer a problem you have this quarter. A permanent search runs two to four months before the successful candidate starts working a notice period.

Scroll the chart sideways.

Weeks from the decision to somebody working An interim starts within half a week to two weeks. A fractional CFO within one to three weeks. A full-time CFO takes eight to sixteen weeks to search and a further four to twelve weeks of notice, so twelve to twenty-eight weeks in total. 0510 152025 Weeks from the decision to somebody working Interim Half a week to two weeks Fractional One to three weeks Full-time Search, 8 to 16 weeks Notice, 4 to 12 weeks Twelve to twenty-eight weeks before the seat is filled.
The bars are drawn to the top of each range. A full-time appointment cannot answer an urgent problem, which is why an interim running alongside a permanent search is a common and sensible sequence rather than an admission of failure.

What each one is actually for.

The same four questions asked of all three. Read across a row rather than down a column, and the choice usually makes itself.

Interim

Cover. A seat existed, and it is empty.

Buy it when
Somebody has left or given notice, a lender or an audit will not wait, and the month has to close regardless.
Priced on
Presence. A senior day rate across most of the week, so it lands near a permanent salary.
Needs
A defined end, and a decision about what should exist on the last day.
Goes wrong when
The problem was structural. Twelve steady months, and the business ends where it started.

Fractional

Capability. There was never a seat.

Buy it when
The work a CFO would have done has been absorbed by whoever had capacity, usually the founder, and the decisions are getting harder.
Priced on
The decision calendar rather than the working week. Compared against the cost of the decisions being made without it.
Needs
Somebody doing the day-to-day underneath. Ownership without execution turns a CFO into an expensive bookkeeper.
Goes wrong when
The problem was cover. The design is sound, then something breaks on a Tuesday and nobody is in the building.

Full-time

A job. Running it fills a week on its own merits.

Buy it when
There is a team to manage daily, several entities with daily operations, and obligations arriving faster than anybody can batch them.
Priced on
Salary, bonus, long-term incentives, employer cost and a search fee. The last two are routinely left out of the comparison.
Needs
A strategy stable enough to plan twelve to twenty-four months against. You are hiring for a direction, not a moment.
Goes wrong when
The function did not need managing full time. A senior person builds the missing thing in six months, then looks for work that justifies the seat.

Six questions, if you want the path.

Work down them and stop at the first outcome you reach. Two of the seven answers are not a hire at all, and one is to go and find a better accountant. None of them asks what you can afford, because affordability decides how deep an engagement runs, not which kind of person the business needs.

Question one

Has somebody left, or given notice?

Yes
An interim Cover is a presence problem, and an interim can be in the building inside a fortnight. Work through the rest anyway: this answers who holds the seat now, not what should exist when the cover ends. Cover and capability are not the same purchase.
No
Nothing has emptied. Go to question two.

Question two

Are the statutory filings late or wrong?

Yes
An accountant Or a better one. It is the cheapest thing on this page to fix. Buy nothing else until the filings are clean, because everything above them is built on them.
No
Go to question three.

Question three

Is one person inside the business closing the month?

No
A financial manager Somebody whose job is the month, the ledgers and the controls. Decide what the function should look like before you write the advert, because a person hired into an undesigned function builds what they already know. The order matters more than the hire.
Yes
Go to question four.

Question four

Does the month actually close, on time and right?

No
A design job, not a hire Somebody already owns the month and it still does not work. Adding a person makes the function larger rather than better, because what is missing is a design and an owner rather than capacity. Fix the shape first: what closes when, who checks what, and what the numbers are supposed to answer. This is the Fragmented Finance Tax, and it compounds quietly.
Yes
The information is sound. Go to question five.

Question five

Do the numbers you already have answer the decision in front of you?

Yes
A day of your own time, not a hire The numbers already answer it and nobody has sat down with them. Block a day with whoever closes your month, put the three decisions in front of you on the table, and work each one through what the business already produces. If that settles them, you have bought nothing and lost a day.
No
They need a view about what happens next. Go to question six.

Question six

Is running the finance function itself a full-time job?

Yes
A full-time CFO A team to manage day to day, several entities with daily operations, and obligations that never stop arriving. On two conditions: a strategy stable enough to plan twelve to twenty-four months against, because you are hiring for a direction rather than a moment, and a start made now, because the search and the notice period run to six months between them.
No
A fractional CFO The function needs owning rather than attending, which is what a fractional CFO is for. The depth moves with the business, from a few days a month at earlier stage to three or more days a week where it is scaling hard. Who is accountable for the whole does not move, which is why this is one model rather than a smaller version of a bigger one.

One thing overrides whatever you reached

If there is a raise, a sale, a facility, or a second country inside the next twelve months and you could not say today which way the numbers point, the timing moves forward. Every one of those tests the finance function from the outside, on somebody else's timetable, and getting ready takes months rather than weeks.

Not sure whether the business has outgrown the way it is run today? Run the eight-statement readiness check.

If the answer was a CFO.

Spurwing owns your finance function, which is the part the title never tells you anything about.

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