Stayed on Jobseekers three weeks too long by mistake,

I have recently returned to Ireland after having left the country 3 years ago and have been forced to try and claim Joseekers allowance. About 5 years ago I stayed on the dole about three weeks too long waiting for my first paycheck to arrive.
After I had secured a job last time the revenue sent me a letter to say I owed them approximately 600euro. I didn't pay it as I assumed it would simply come out of my PRSI and tax. Will I be approved this time? Im broke and at my wits end. Any help much appreciated. Advice needed.
many thanks

Do you mean you got a letter from Social Welfare regarding the overpayment? It's possible that the overpayment is still on the books - if it is, repayments will be deducted from any jobseeker's payments you will get.

The fact that there is an overpayment shouldn't affect your entitlement, you will be assessed (means-tested) as normal.

I got a letter while I was working to say that I had been overpayed. I didn't sign off soon enough, simply because I couldn't I was broke and needed to stay on it a few weeks until I got paid from my new employment ( all this was 4 years ago ).
I went abroad for 3 years and returned 4 weeks ago, I signed on immediately, the welfare then sent me for a means test which I completed and am now waiting for approval. I totally forgot about the overpayment 4 years ago and am bricking it now.

There are two separate things here. Social welfare has been dealt with. Revenue are separate. They wrote you a letter stating you owed them 600 which you did not pay. But if you left in the middle or so of a tax year where you had paid tax in all likelyhood you would be due some tax back which can be offset against the 600. You need to contact revenue to see what the situation is.

Has social welfare been sorted though. If the op did not sign off for three or four weeks after they had started work, then they owe that money back to Social Welfare as well.