how do i default on a loan?

Answer 1

don't pay it back

Answer 2

That's a weird question.... You will default on your loan when you STOP paying for it and continue to stop paying for it.

When you first miss your payment, they will send you a warning and late payment penalty. At this point, you are technically already default, but most companies will usually give you a benefit of doubt. They will keep asking you to pay. Eventually, they will stop asking you to pay and send you for a collection. When you still don't pay, you will be considered default and they will try to send you to court and obtain a judgement against you for whatever they can collect.