A loan from a 401(k) is not a distribution and does not get reported on a tax return.
No, not unless you default on payment, leave your employer without paying in full or even change jobs. This isn't a distribution just yet. And may never become one unless you fail to pay back or change jobs with rules, for example.
According to the IRS:
Your 401(k) plan may allow you to borrow from your account balance. However, you should consider a few things before taking a loan from your 401(k).
If you don’t repay the loan, including interest, according to the loan’s terms, any unpaid amounts become a plan distribution to you. Your plan may even require you to repay the loan in full if you leave your job.
Generally, you have to include any previously untaxed amount of the distribution in your gross income in the year in which the distribution occurs. You may also have to pay an additional 10% tax on the amount of the taxable distribution, unless you:
Any unpaid loan amount also means you’ll have less money saved for your retirement.
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