Professional fees are what you pay for expertise you do not carry in-house: accountants, bookkeepers, solicitors, consultants.
The cost of buying too little
This is the line owners cut first and pay for indirectly.
A bookkeeper you did not hire shows up as a year of uncategorised transactions, a tax return built on guesses, and a set of figures nobody can make decisions from.
A lawyer you did not consult shows up as a contract that did not protect you, or an employment classification assessed backwards with penalties.
An accountant you only see at year end shows up as tax planning that could not happen, because by then the year is closed.
Getting more from what you already pay
Most owners use their accountant for compliance and nothing else. The higher-value conversations are the ones they are rarely asked for:
Before a large purchase, not after. Before hiring, on structure and classification. Quarterly rather than annually, so the year can still be changed.
Arriving with clean books and a specific question costs less of their time and produces better answers — see tax documents and packages.
Where it sits
Professional and banking in your accounts, as overhead. Genuinely variable in a way most overhead is not: it rises with complexity — more entities, more locations, more staff — rather than with revenue.