Not just for the end of the year, but I check that I’ve paid enough in taxes. Roth conversions (for US folks), investment income in taxable accounts, retirement distributions, etc can all generate taxable income that pushes tax liability too far above the amount covered by payroll withholding and result in penalties.

Edit: Specified that Roth conversions are for US folks

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you forgot about the hundreds of annual changes Congress makes to the tax code that the IRS is tasked with implementing

I find the temporary containers extension essential. Set automatic mode and forget.

this is the portable solution