HMRC said changes to helpline services to encourage people to go online first have been successfully trialled over the past year and are being rolled out to become a permanent feature from April 8.
The changes mean that, between April and September, the self-assessment helpline will be closed and customers will be directed to self-serve through its online services.
But the chairwoman of the Treasury Select Committee, Harriett Baldwin, said the move to online services should not be “forced on taxpayers”.
She said the revenue body has not yet demonstrated that the department or the public “are ready to make such a monumental change to how they resolve tax issues”.
Ms Baldwin said: “It is a great shame that HMRC have decided now is the time to essentially close down any avenues for people to contact them over the phone for huge parts of the year. I say once again, these are well-meaning people just trying to get their taxes right.
“We’ve heard time and time again that every effort is being made to direct people to resolve issues online.
“The committee welcomes efforts to make the tax system more efficient but HMRC has not yet demonstrated that the department or the public are ready to make such a monumental change to how they resolve tax issues. This should not be forced upon taxpayers until there is evidence that people know how to do their taxes on HMRC’s incredibly complex website.”
Between October and March, the helpline will be open to deal with priority calls, and customers with queries “that can be quickly and easily resolved” online will be directed to HMRC’s online services.
The VAT helpline will be open for five days every month ahead of the deadline for filing VAT returns.
The PAYE helpline will no longer take calls from customers relating to refunds, and customers will be directed to use HMRC’s online services.
HMRC advisers will continue to always be available during normal office opening hours to support customers who cannot use online services or who have health or personal circumstances that mean they need extra support.
It added that all other helplines will continue to operate as they do currently.
The revenue body said the move to online self-service for self-assessment and VAT is a vital element of HMRC’s modernisation of the tax system.
It said customers can access information more quickly and easily by going online or to the HMRC app.
Angela MacDonald, HMRC’s second permanent secretary and deputy chief executive, said: “Online services have transformed our lives and often provide a better service for managing tax – they’re quicker, easier and always available.
“Changing our services to encourage customers to self-serve online wherever possible will allow our helpline advisers to focus support where it is most needed – helping those with complex tax queries and those who are vulnerable and need extra support.
“We must maximise every pound of taxpayers’ money. Embracing online self-service allows us to help more customers and improve our customer service levels without spending additional public money.”
Tina McKenzie, policy chair at the Federation of Small Businesses (FSB), said: “This news will be greeted with dismay by thousands of small businesses. If you don’t have a dedicated tax and finance expert on hand, as many small businesses and self-employed people don’t, tax queries can rapidly turn into huge headaches.
“We all know that chatbots and exhortations to go to a particular website for information are in many cases no substitute for talking to a real person, especially for complex or time-pressured issues.”
The Chartered Institute of Taxation (CIOT) described the changes as “misguided”.
CIOT president Gary Ashford said they were “deeply dismayed”.
