In the US taxpayers track their charitable giving and use it to reduce their taxable income at filing time.
In the UK when you donate to a charity you attest to that charity that you are a UK taxpayer and that the donation is therefore gift aid eligible, and the charity just goes to the tax office and collects an extra 25% on top of the donation.
So in the US, say, you earn $150, pay $50 in tax withholding, then donate $100 to a charity, then claim the donation to the IRS to say you shouldn’t be taxed on $100 of your earnings, so you should only have paid $30 in taxes, and you claim back $20. You have $20, charity has $100, taxman has $30.
In the UK you earn £150, pay £50 in PAYE, then give £80 to a charity, keeping £20 and telling the charity they can giftaid it. Charity goes to the taxman and asks for another £20. End result, you have £20, charity has £100, taxman has £30.
Essentially the same outcome - charity donations are tax advantaged - but the paperwork for taxpayers is much simpler.
UK equity: smart people use an ISA wrapper https://www.gov.uk/individual-savings-accounts/how-isas-work or a pension, both of which are tax free for people with normal incomes and wealth.
Selling online: after £1000 you're a "trader" and have to pay tax. https://www.gov.uk/government/publications/selling-online-an...
That takes care of almost everything. My employer paid me a bonus in RSUs and doing so was also automatically accounted for in PAYE. However, this discussion has reminded me to sell the vested stock and move it to an ISA rather than leave it in a US ETrade account, to simplify future taxes.
My wife, a UK national resident in the UK, sells ebooks on Amazon as a side gig. She has to file notice to the _US_ tax authorities for exemption, because Amazon assume everyone is American for tax purposes.