HM Revenue and Customs is setting £45 million aside to improve customer service after figures show that 7.2 million phone calls made to it in the last year went through to a 'busy' tone instead of the caller being able to speak to someone.
Between April 2014 and March 2015, 64.7 million calls were made to HMRC but only 72.5% of these were answered, falling short of the revenue body's target of 80%.
Meanwhile, more than one in 10 (11%) call attempts made last year went straight to a busy tone, with around 7.2 million call attempts ending this way.
Some months were particularly stretched, with as many as one in five (20.8%) customers hearing a busy tone and being unable to join a phone queue in September 2014.
HMRC says calls tend to peak around key deadlines, such as 31 January for self-assessment and 31 July for tax credit renewals.
MoneySavingExpert.com has long warned people about HMRC's slow answering times around key deadlines and has campaigned for it to do more about it.
Lin Homer, HMRC chief executive, says: "Despite our best efforts, our call performance hasn't been up to scratch, and we apologise to all those customers who have struggled to get through to us."
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Where does the money come from and where will it go?
The £45 million allocation will come from the current spending settlement and is not additional revenue from the Treasury, HMRC says.
The money is paying for around 3,000 additional staff to join customer service teams, on top of around 2,000 who are being moved over temporarily from other parts of HMRC to help with the tax credits deadline and letters and forms.
Homer adds: "We have also invested in new telephone equipment, which lets us switch calls to many more offices, not just take them in contact centres, so more of our staff can help customers at the busiest times.
"Our new online services are also giving customers new and better ways to deal with HMRC, and I urge all customers who can go online to do so. For services like tax credits, it's quick, simple and can be done anywhere, anytime, including from a smartphone."