Tax and overpaid socialwelfare

I was out on sick leave last year and I don't get sick pay by my company. I claimed illness benefit and I handed in a final cert to the social welfare office when I was well enough to go back to work.
I was overpaid by a number of weeks. I contacted them to let them know this.
I arranged to pay it back over the course of 5 months.
I have been looking to do a p21 balancing statement for last year, and i can see my social welfare payment is on my file, however it includes the overpayment which I have now paid back.
I believe I have overpaid tax last year due to my illness etc. Would this overpayment would affect any refund? Do I need to contact Social welfare so I can get my tax sorted properly? I paid some of it back last year ( december) and the rest my monthly standing order between Jan and april this year.

thanks any help appreciated