A Saturday in late February, 4:10 p.m. A business owner calls your firm about a partnership return due in March. A friendly agent at the answering service answers by the second ring, jots down who called, their number and a short note, and emails it to the office. The note is waiting when the front desk unlocks the door on Monday at 8:30. By then the caller has a meeting booked at the firm whose phone offered a time.
Both routes answered that call. What differs is what the caller had when they hung up, and what the month cost. This post compares an answering service for a CPA firm, with live agents whose bill counts calls or minutes, against an AI receptionist sold for one flat monthly price. It works through one firm's February after-hours calls. Put your own phone log in place of ours and the answer becomes yours.
Where live agents earn their fee
A good service puts a trained person on your line whenever nobody at the firm can pick up. Callers hear a human voice, and some callers will talk to nothing else. An agent can calm an upset client, follow someone who rambles, and write a messy story down in plain words.
Many services can also patch an urgent call through to an owner, and some can book into a shared calendar. For a firm whose after-hours callers are mostly long-time clients happy to leave a message, that may be plenty.
The limits come from what the agent knows. Unless you hand over your fee list, your hours and your what-to-bring list, the agent can only take a message. Nobody at the service can see where a client's return stands.
Where the AI earns its place
An AI receptionist picks up every call at once, at 7 p.m. or 2 a.m., and two callers ringing together don't queue. Its first words tell the caller they have reached the firm's AI helper, so nobody is misled.
Its answers come from what your firm wrote down: hours, the fees you publish, what to bring, where to upload. It books an intro call or a drop-off into your calendar and confirms it by text. It can switch to Spanish halfway through a sentence. Every call leaves a transcript and a two-line recap for the morning.
Its limits are real too. Some callers hang up the moment they hear an AI. It knows only what your firm gave it, so an odd question turns into a call-back. And it gives no tax advice, ever.
How answering services bill
Pricing for live answering services mostly follows two models. Each vendor's current pricing page has the numbers; write down the date you read it, because plans change.
Per call. Each answered call counts once, whether it lasts twenty seconds or six minutes. Ask how hang-ups, wrong numbers and spam calls are counted.
Per minute. You pay for the agent's time with your caller. Ask whether each call is rounded up to a whole minute, and whether the time spent writing the message or transferring the call counts.
Either kind can come as a monthly plan with a fixed allowance of calls or minutes, plus a rate for each one beyond that. Before you sign, ask what is billed apart: booking into your calendar, Spanish-speaking agents, holidays, setup.
How AI receptionists bill
AI phone answering comes in two pricing shapes as well. Some vendors charge by the minute, much like a live service. Others sell a flat monthly plan, where the price holds however busy the phone gets. Here we compare the flat kind, because tax season is where the two part ways.
One firm's February, after hours
Take a four-person CPA firm, open 9 to 5 on weekdays. The numbers below are an example shaped like a small firm's February, not a survey. Swap in your own from your phone log.
That February, 64 calls came in before 9, after 5 or on a weekend. They ran about three minutes each. Sorted by what the caller wanted:
| What the caller wanted | Calls |
|---|---|
| Is my return done? | 18 |
| Hours, what to bring, where to upload | 16 |
| A prospect wanting a first meeting | 12 |
| Urgent: an IRS letter, a deadline | 6 |
| Hang-ups, wrong numbers, spam | 12 |
The test for each route is the same. What did each of those 64 people have when they hung up, and what did February cost?
The per-call math
All 64 calls count, the twelve hang-ups included, unless your agreement says otherwise. Multiply 64 by the per-call rate on your quote, then check it against the calls your plan includes.
What the firm gets back is about 52 messages for Monday. The 18 status callers still need a call-back, since the agent can't see your board. The 12 prospects need one too, and by Monday a few will have booked somewhere else. The 6 urgent callers reach someone only if the service patches them through to a phone you named.
The per-minute math
At three minutes each, 64 calls come to 192 minutes before any rounding. Multiply by the per-minute rate and add the plan's monthly minimum, if it has one.
The result looks the same as per call: messages, not bookings. The bill follows the calls, so it climbs in exactly the weeks your phone rings hardest, which at a tax firm means the run-up to each deadline. July is cheap. March and April are not.
The flat-plan math
The same 64 calls, at the price you pay in July. Here is what each caller had when the line went quiet.
The 18 status callers hear where their return stands on your board, as long as they ring from the number on the client's record. Anyone else hears that staff will call them back. The 16 routine callers get the answer from your own list. The 12 prospects end the call with an intro call on the calendar and a confirming text. The 6 urgent calls ring the preparer you set as on call, with a recap of what was said. Monday opens with a page of recaps, and most of the follow-up is already done.
One example: AccrueNest's price depends on headcount, starting at $97, and each plan includes round-the-clock AI call answering.
What neither one should do
No agent and no AI should give tax advice. Nobody on an after-hours line should tell a caller what they owe, what they can deduct, or whether a return is ready to file. A preparer gives those answers.
The AI should say plainly, before anything else, that it isn't a person. Recorded calls should play a notice first, whoever answers. And nobody on the line, human or AI, should collect Social Security numbers or bank details over the phone.
Which one fits your firm
Go back to your own February table. If most after-hours callers are long-time clients who'd rather hear a person, and a message is enough, a live service fits. Its bill also shrinks in the quiet months.
If many are prospects and routine questions, and you would rather start Monday with meetings booked than messages to return, a flat-plan AI fits better. Some firms run both: their own people answer first during the day, and the AI covers nights and Saturdays. Either way, calls that take judgment still go to a preparer.
AccrueNest
AccrueNest sets up the calls, texts, organizers, letters and marketing for US accounting firms of 1 to 10 people. We write up the questions firms put to us, with the arithmetic shown.
