On 31 January 2025, HMRC received 732,498 Self Assessment returns in a single day. The busiest hour was four to five in the afternoon, when 58,517 people filed. Another 31,442 filed between eleven and midnight.
Those are HMRC's own published figures, and they describe your January. Every one of those last-minute filers who uses an accountant generated calls, emails and chasing in the weeks beforehand, and a good share of them rang on the day.
HMRC's performance data shows the same spike on its own lines. It took 2.958 million calls in January 2026 against 2.052 million in December, roughly 44% higher and the highest month of the year. Of January's adviser call attempts, 328,000 went unhandled. Nearly 45% of callers waited more than ten minutes. Satisfaction with its phone service ran at 58.7% that month against 80.6% for digital services.
If the organisation with 800 phone advisers on deadline day struggles with January, a practice with one person on reception has no chance of handling it by working harder.
The shape of the problem
Accountancy call volume is not steady. It has a pronounced peak that everyone in the practice can predict and nobody can staff for.
HMRC reported that with under a month to the 31 January 2026 deadline, 6.36 million returns had been filed and almost 5.65 million were still outstanding. That backlog turns into client contact: documents chased, questions asked, payments queried, panic calls from people who left it late.
There are secondary peaks through the year. The 31 July payment on account, corporation tax deadlines, the run-up to 5 April, quarterly VAT.
Staffing for the peak means carrying cost for eleven months. Staffing for the average means the phone rings out in January, which is when your clients are most anxious and most likely to remember how you handled it.
What answering software does about it
It answers every call regardless of volume. Fifty calls arriving at once are handled at the same speed as one. That is the whole argument in a sentence: the peak stops being a staffing problem.
It covers the hours people actually ring. Evenings and weekends, when clients sit down with their paperwork. HMRC's data shows deadline-day volume running until midnight, and the 2025 deadline fell on a Saturday.
It handles the repetitive questions. Which documents do you need, have you received my paperwork, when is the deadline, how do I pay, what is my reference, have you filed yet. In January these are the majority of calls, and they are all factual.
It takes structured messages. Client name, what they are chasing, deadline exposure, whether it is urgent. Consistently, so whoever picks it up is not starting from nothing.
It filters. January is also when software vendors and recruiters ring. Filtering those frees more time than most practices expect.
It stops partners answering reception calls. In a small practice in January the senior people end up on the phone because it will not stop ringing. That is the most expensive possible use of their time in the month their chargeable hours matter most.
What still needs a person
Anything about a specific client's tax position: whether a cost is deductible, what their liability will be, how to treat a transaction. Software must refuse this rather than attempt it.
Anything involving figures on a return. No estimates, no confirmations, no reading balances back to a caller.
HMRC investigations, penalties and enquiry letters, where the client is worried and the detail matters.
Money worries. A client who cannot pay needs a conversation about time to pay, not a booking link.
Anyone distressed. Late January produces genuine anxiety, sometimes about large sums.
And new client enquiries you want to win. These convert on the conversation. Capture the details by all means, then get a person to ring back the same day.
What it costs against temporary staff
A temporary receptionist at £14 an hour, covering 37.5 hours a week for five weeks, costs roughly £2,600 plus agency fees. That is one person covering office hours only, who needs training in the first week of your busiest month.
Answering software runs from £49 a month for 25 answered calls, £179 for 100, £399 for 250. It covers evenings and weekends, needs no training in January because it was configured in November, and does not leave in February.
Two honest points. Temporary staff can do things software cannot, including judging which calls matter and chasing clients proactively. And a service you configure in the last week of January will not work properly, because nobody has had time to tell it what your practice does.
Confidentiality and data
Client financial information carries obligations, and a supplier holding your call recordings holds some of it.
Ask where the data sits and for how long, and get it in the contract. Ask directly whether recordings are used to train models; some suppliers do this by default. Get a data processing agreement, which UK GDPR requires where a supplier processes personal data for you. Check your professional body's rules on third-party suppliers, whether that is ICAEW, ACCA or AAT. And ask for security certificates rather than adjectives.
Keep the amount of information the system collects small. Enough to identify the client and route the call. There is no reason for a phone system to hold detail about a client's tax affairs.
Getting ready before January
October. Pull your call data from last January. How many calls, at what times, on what days, about what. Sample the voicemails. This is your specification.
November. Configure. Load your FAQs, deadlines, document lists, payment details and areas of work. Connect the diary. Write down which calls go straight to a person, and to whom. Guided setup matters here: a dashboard handed over with no help tends to sit half-finished until it is too late.
Early December. Test with awkward calls. Have colleagues ring as a client asking whether something is deductible, a client who cannot pay, and someone with a penalty letter. If the system attempts an answer on any of the three, fix it before January.
Late December. Divert out-of-hours calls first. Low risk, immediate benefit, and it shows you how the system behaves before the peak.
January. Read transcripts daily for the first week. Every missed question is a configuration gap. Keep a named person as the escalation route, and make sure they know they are it.
February. Review what it handled, what it got wrong, and what clients said. Adjust for July.
The point
The January peak is the most predictable operational problem in accountancy and the least solvable by effort. HMRC handles it with hundreds of extra advisers and still leaves 328,000 calls unhandled and 45% of callers waiting over ten minutes.
A practice cannot out-staff that curve. What it can do is take the repetitive calls off its people entirely, so the questions that need an accountant reach one quickly, and partners are not answering reception calls in the month their time is worth most.
Set it up in November. A service configured during the crunch is a second problem, not a solution to the first.