GPs trying to upload annual certificates or self-assessment pension forms on the 28 February deadline day reported receiving error messages.
A Capita spokesperson admitted that the service's online enquiries form had experienced 'some intermittent issues due to the volume of traffic on the website' but that the site was now working.
A message posted on the enquiries form page of the PCSE website on Thursday said: 'Due to the high volume of traffic to our online enquiries form, some users have been experiencing intermittent issues with the submission of pension forms.
'We are monitoring this closely and addressing any issues as quickly as possible. If you do receive an error message when completing or submitting the form, please try again later. As a result, we have extended the deadline for submissions to until 5pm on Monday 4 March 2019. We apologise for any inconvenience.'
Hi @capitaplc - I'm just trying to submit my end-of-year pensions form via your website. This keeps happening. Could you please let me know asap when your website will actually WORK? #NHS #Pensions #Capita #PCSE pic.twitter.com/0j4pjZMbiZ— Nicholas Grundy (@nick_grundy) February 28, 2019
Problems with the submission of pension forms are the latest in a long line of problems with the PCSE service since it was outsourced to Capita in 2015.
GP leaders have repeatedly called for the company to be stripped of the PCSE contract, and for the service to be taken back in-house by the NHS.
Just under a year ago, GP leaders hit out at 'scandalous' delays for pension payments to GPs - and in September 2018 NHS England launched a review of all GP pension data after identifying discrepancies between contributions and pensionable earnings.
Last summer, an influential committee of MPs said that NHS England's decision to outsource PCSE to Capita was a 'shambles', while the National Audit Office said the £330m deal was 'high risk' and threatened serious harm to patients.
Capita has previously apologised for 'unacceptable failings in relation to the initial delivery' of its PCSE contract and has said it remains committed to delivering it.