The HM Revenue & Customs (HMRC) Self Assessment (SA) tax helpline will close from 12 June until 4 September 2023, with users directed to digital tools.
The government department said the move will free up 350 advisers to deal with urgent queries during a time when the helpline receive "far fewer calls".
According to HMRC, calls are around 50% higher between January and April compared with June to August.
During the telephone line's closure, HMRC said available advisers will be increased on the Self Assessment webchat, the online service helpline and the extra support team helpline.
Angela MacDonald, deputy CEO and second permanent secretary at HMRC, said:
"We continually review our services to see how they can best serve the public and we are taking steps to improve them.
"A seasonal SA helpline will make more of our expert advisers available where they are most needed during the summer months.
"Our online services, including the HMRC app, are quick and easy to use and have been significantly improved. I urge customers to explore these fully before deciding to wait to speak to us on the phone.
Update on 13 June 2023
Harriett Baldwin MP, chair of the Treasury Committee, has written to Angela MacDonald, HMRC's deputy chief executive, about the decision to close the Self Assessment helpline.