HM Revenue & Customs switched off 19 key online services, the majority over the whole weekend, in order to test an undisclosed future upgrade to its systems.

Services were switched off from 6am on Friday right through to 6am on Monday this week. They included the pay as you earn system, stamp duty, VAT online and individual self-assessment. Corporation tax systems were switched off earlier, Thursday at 5pm.

The child trust fund, pension schemes, construction industry scheme, EC sales list, employee share scheme, new computerised transit system, new export system, reverse charge sales list, online agent authorisation, and shared workspace scheme, were all affected.

People trying to log in to the majority of those services during the weekend were shown a message saying that they were unable to register for the service, or that they were only able to access the service if they used their own software, rather than HMRC-supplied software.

There were also problems with those attempting to download the new corporation tax software provided by HMRC. For many of those using the Microsoft Internet Explorer browser, an adjustment to the settings was necessary.

HMRC declined to state what upgrades it was making, or when they will go live, but added that they were all “scheduled”. It is thought they could be targeted to go live before the new tax year begins at the end of April.

The changes may be part of an ongoing transformation programme to standardise and simplify systems at HMRC. That programme is also aimed at improving customer service and transactional speed, as well as improving data management.

A spokesperson said: “This weekend saw HMRC deliver changes to how our customers access some of our online services. This meant some services were not available over the weekend and we told people about this on our web site.”

In October, HMRC announced that it had renegotiated some of the terms on its £8.5 billion Aspire contract with supplier Capgemini, focusing on saving a further £110 million annually, in addition to the £70 million agreed two years ago.

In order to achieve the savings, it is standardising systems onto “common industry components”, and simplifying and modernising its technology. It is attempting to better integrate its software. Fujitsu and Accenture are subcontractors on Aspire, which runs until 2017.

Following HMRC’s loss of 25 million people’s details on two computer discs in 2007, a government review found the department had "fragmented" and complex IT systems that made it difficult to identify and manage its information.

In June, the powerful Committee of Public Accounts rebuked HMRC for its inability to create an affordable system with a single view on each taxpayer. The department was also criticised for signing a compensation agreement with supplier EDS, over the failed tax credits system, that guaranteed EDS future contracts.