Surely if tax isn't raising enough money, a government could just print some more and sort itself out that way? The main problem with this idea is that it might cause inflation, where the actual purchasing power of a unit of currency falls, because its value has decreased. According to most economists, the more the general level of prices goes up, the less one unit of currency can get you, so the more its value falls.
Why would this happen? The idea is that creating money that didn’t exist previously means that there’s more money as a whole in circulation, which makes each individual unit worth less. That means that prices should rise, as sellers realize that they need to earn more from their goods to be able to afford the same lifestyle they’re used to, because the money they’re earning is worth less. In other words, their purchasing power has gone down.
Economists don’t agree on the best way to handle inflation, or even on the details of why it happens. When Western governments started using a policy known as quantitative easing after the 2008 financial crisis, electronically printing tons of money to stimulate the economy, some economists warned that a disastrous amount of inflation would hit the economy—but it never happened.
Obviously this doesn’t mean everyone should print as much as they want; it just means the ins and outs of when printing money works, and when it doesn’t, aren’t as black and white as economists might hope.