From April 2023.
Most people tend to think of IR35 being for those incredibly expensive contractors who turn up in suits every day (well T shirts on Teams these days), to collect their exorbitant fees from the client.
In fact the biggest impact of the 2021 IR35 change would be your Amazon and DPD drivers and your local "hand car wash" owner. The government has spent most of the last decade forcing clear self employed staff into limited companies. Then hammered them with IR35 and turned them into employees paying a net 62% of their income in taxes and NI.
This huge turn around in Kwarteng's mini budget will have huge ripples through the employment market. Not least of which is that I can stop telling every agency that has a "critical" and "Urgent" need for an IT security project manager that I don't work under IR35 and that they'll just have to go and find another PM who can help them fix their HUGE security holes. Including all those Government departments who kicked off all those security projects in the last year....
More importantly Truss just unlocked between 0.5m and 1.5m votes and made them more disposed to voting for her at the next election. I expected some moves but the moves they made have been dramatic; to say the least.