"The way to fund £20bn of extra healthcare spending is for the government to create the necessary funding for that purpose. And it can do this at any moment. The fact is that tax does not precede spend. It is always, and inevitably, true that spend precedes tax.  In that case the hypothesis that extra tax must be raised before the NHS can be funded is incorrect. What actually happens is that if the government spends an extra £20 billion into the economy, and increases GDP directly as a result (because government spending is part of GDP, because it creates wealth) then  the government can, if it so wishes, claim back some, all, or even more of that spend in tax  if it so wishes."
http://www.taxresearch.org.uk/Blog/2018/10/11/we-dont-need-tax-to-fund-the-nhs-but-we-may-increase-taxes-because-we-do/