Universal credit

If caught it’s benefit fraud , they will order you to pay back

An overpayment letter might be issued and they would recover any amount you weren't entitled to. If you continue to not disclose it you could be prosecuted for fraud.

@Becca I have declared it. I honestly thought they had access to my bank and did assessments every month

It should be fine. It's quite common actually. You've declared it and that's all you can do. It is unlikely that any further action will be taken. UC won't have access to your bank account unless you're asked to provide statements as evidence for something (the UC Review team is requiring this at the moment but you would be notified and it's a standard check for claim changes since covid). Earnings are recorded through HMRC which is how they get earnings calculations. I would recommend updating it regularly to make sure that it is accurate on your UC. If the savings go down it won't automatically update.