[sokoloff]

> Most people’s entire income is a single W2, and their payroll provider should be able to deduct the exact amount down to the penny.

People also like to get steady paychecks. In any progressive tax system, anyone who leaves a job mid-year would either mean everyone would have to have paychecks that varied or job changers would have a discrepancy at the end.

Having paychecks varying due to taxes would no doubt be spun by some as “theater to make you hate you taxes”.

Homeowners with mortgages probably don’t want to share those details with their employer, out of some combination of “it’s none of their business” and “could they use that information against me somehow?”

I get that filing taxes is annoying, but trying to set things up so my payroll department eliminates that seems the wrong path versus making the front door to the filing system easier to use.

[pjc50]

> anyone who leaves a job mid-year would either mean everyone would have to have paychecks that varied or job changers would have a discrepancy at the end

The UK "P45" system mostly avoids this? If you go from pay £X to pay £Y it's not impossible to calculate how much you will owe at the end of the year and distribute that over the remaining paycheques.

[sokoloff]

(It looks like it does/could.) I'd much rather file taxes than give the details down to the penny of my prior pay from employer 1 to my new employer 2 (which is what I think the P45 system does).

But that probably reflects more my own stance on personal and financial privacy than on anything fundamentally negative about the practical value of preserving that privacy.

[nsteel]

And in the case where you don't/can't provide a P45 they take an "emergency" high rate of tax instead. Which you can claim back once the information is provided, or at the end of the tax year. I don't know if you can legitimately decide to not provide a P45 for some personal reason, but it could be an expensive decision (in the medium term).

I would say this definitely reflects your personal stance on privacy, I think most people would rather have the money they earned sooner rather than later.