Not always. If you are a sole trader subcontractor working for one or two contractors, a good general accountant will do everything you need and cost you less. Anyone telling you otherwise is selling.
The answer changes the month you start paying subcontractors yourself.
The moment it changes
Paying subbies puts you inside the Construction Industry Scheme as a contractor. From that point you have a monthly filing obligation, a verification obligation before every first payment, and personal exposure if the deduction is wrong.
That is not a bolt-on to normal accounting. It is a recurring compliance job with penalties attached, and it runs alongside a VAT regime that only applies to construction.
Four signs you have outgrown a general practice
Your CIS returns go in late, or you file them yourself. If it is on your desk rather than theirs, you are paying for compliance you are still doing.
Nobody has ever reconciled your CIS suffered against HMRC’s record. If they claim off your bookkeeping alone, there may be money sitting there that nobody has looked for.
Retention is not on your balance sheet. Have a look. If money you have earned and not been paid is missing from your accounts, your accounts are wrong.
You cannot say which jobs made money. If the answer only arrives in the annual accounts, it arrives too late to change anything.
What a specialist is actually worth
Not the compliance. Both do that.
It is the reconciliation nobody else runs, the 5% VAT rate caught on a conversion, the retention chased rather than forgotten, and knowing a job is losing money while you can still do something about it.
On a £2 million business, any one of those tends to cover the difference in fees on its own.
When to stay where you are
If you are under a few hundred thousand, not paying subcontractors, working for one main customer, and your accountant answers the phone, stay. Changing accountants costs time and goodwill and there is nothing here worth it yet.
We have said as much to people who rang us wanting to switch.
What switching involves
Less than people expect. You tell your current accountant, we write to them for the handover, and the records come across. It normally takes a fortnight and you do very little of it.
The best time is just after a year end, because you start clean.
How to decide
The honest test is whether the things above are costing you anything. If retention is tracked, CIS is reconciled and you know your job margins, a specialist adds nothing you are not already getting.
If two or more of them are missing, the gap is probably bigger than the fee difference.
More detail in specialist against general practice, or see whether we are a fit.