Can I sue someone over a personal loan if we never wrote anything down?

A verbal loan is enforceable, and people assume otherwise far too readily. What the absence of paperwork actually costs you is a year of runway and a different way of proving the case. The window narrows from four years to two, counted from whenever the money was meant to come back and did not, and that combination bites hard because informal loans are exactly the ones people let drift longest. Nothing sits in a system reminding anyone, so a friend who was going to sort it out next month becomes a friend you have not chased in three years, by which point the claim may be gone.

Proof is more attainable than it sounds, because money almost never moves in complete silence. The transfer itself is documented by whoever handled it, and around it there is usually a trail: the message asking for help, the reply promising to return it, a follow-up about timing, a partial repayment. Any single repayment is worth more than everything else combined, because handing money back is behaviour that nobody performs in respect of a gift. A person who was present when the arrangement was made also carries real weight here, and small claims is set up so that they can simply attend and describe what they heard, without formal procedure.