As we all know, taxes only ever seem to go up. Not just income tax, but VAT, various duties and Council Tax.
I looked at the trend over the past 100 years and added a trend line. As you can see it is heading upwards:

I then projected this trend forward to find out when taxes would reach 100% of average income and that date was 2353.
Looking at the steeper increases over recent years I ran a second projection based on the trend since 2020 and that brought the 100% date forward to 2154.
Fun thought to lighten the mood:
This puts the UK Government on a trajectory to surpass total income capture well before the 2266 setting of Star Trek, which famously imagined a future that had moved beyond such traditional economic constraints.