Will CU arrears ruin icb rating?

Long story short, I took out a loan with cu. Monthly repayments were x per month and I accidently put x on the form to pay it by dd. So I built up arrears and didn't even realise it. I have now paid these arrears but will this show up on a credit check?

Depends on the cu... have a look here [broken link removed] and get a copy of your credit report from the same site, it will cost €6.00.

If it does show up I would go to the cu and question it. They should have also noticed that you set up the dd for 10e short and told you.