Warning over government IT systems should Scotland vote for independence

£1bn-plus IT bill for Scottish government - including a tax system that will be delivered two years after independence, according to the SNP's own timetable

The IT infrastructure of the entire public sector will be shaken up should Scotland vote for independence - with Scotland paying a £1bn-plus bill to establish its own systems across the whole public sector.

Systems and services giant HP, which currently makes some £140m per month from public sector IT contracts, has already drawn up contingency plans - with a bonanza awaiting computer services companies - should the Scottish electorate vote "yes" on Thursday.

"We're planning for both scenarios. We've got a big presence up in Scotland. We've got to plan either way," Andy Isherwood, HP's managing director for the UK and Ireland, told the Daily Telegraph.

He added: "Everyone has a plan now. I think it will require a massive level of diligence [to separate IT systems]. These things take time."

HP currently runs a major IT centre in Erskine, just outside Glasgow, and it is unclear at the moment what plans HP may have for that in an independent Scotland.

The IT services work will not just involve disentangling the IT systems of the remaining UK (rUK), but also establishing similar systems for a new Scottish government.

The biggest challenge would, perhaps, be in the Department for Work and Pensions (DWP), which is midway through a major project intended to deliver Universal Credit, one of the coalition government's biggest IT projects.

The Treasury has estimated that establishing a new IT system to pay benefits in Scotland will cost about £400m and take four years to implement - being delivered just in time for formal independence in 2018.

The Scottish government would also need to set-up its own systems for tax collection, including income tax, corporation tax and value-added tax. That would cost another £500m and, according to Scottish National Party (SNP) leader Alex Salmond's timetable, would be delivered by 2020 - two years after independence.

On top of that, Scotland would need its own Police National Computer (PNC), which would need to extricate criminal records relevant to Scotland from the rUK's systems. On the other hand, however, IT systems in the health service and courts systems are already independently run and should not require much adaptation.