Irish Water says just over half people have now paid their bill.
Early figures from the first billing cycle of January to March put the compliance rate at 43% – or 675,000 households out of a total of 1.52 million.
That has now risen to 51%, or 775,000 homes.
Bills that cover water usage between April and June are still being sent out.
Minister of State at the Department of the Environment Paudie Coffey said the rate of compliance was growing, and that there was no alternative to paying the bill.
Irish Water call centre staff have begun phoning customers who had not made any payments 21 days after the issuing of their second water bill.