system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do Americans need to file tax returns each year?

Why do we need to submit complicated paperwork to the government each year before we get our yearly net tax refund/bill? Why doesn't the government just calculate how much tax we need to pay for each paycheck based on basic information (salary/wage, pay frequency, state of residence, etc)? It seems that the only reason someone should need to file anything is if he/she had additional things to deduct, such as mortgage interest, student loan interest, or other special items. It doesn't make sense how someone who pays taxes with each paycheck could end up owing the government thousands of dollars more at the end of the year with basically no warning.
gpt
>Why doesn't the government just calculate how much tax we need to pay for each paycheck based on basic information (salary/wage, pay frequency, state of residence, etc)?

Because that's not enough to determine your taxes.

Are you currently a student? Are you paying back student loans?  Are you paying off interest on a mortgage? Did you buy an electric car?  Did you install solar panels on your house?  Did you earn income from gambling?  Did you earn interest on savings accounts?  Did you donate to charity?  Did you have a child?

All of those factors (and many more) will change your tax obligation, and the government needs you to explicitly list whether or not those things apply to you.

>It doesn't make sense how someone who pays taxes with each paycheck could end up owing the government thousands of dollars more at the end of the year with basically no warning.

The only way that can happen is if you **really** screw up your deductions when you fill out the W-4 form that your employer gives you when you begin employment (or fail to update it when you have a change in life circumstances).