Concerns are being raised about how lenders engage with the Help to Buy scheme, which more than 1,100 people have applied for.
Under the scheme, first time buyers can get 5% of the value of a new build or a self-build, to help with the deposit.
As of this morning, just one builder was listed on Revenue’s website as a qualifying contractor.
That number has since risen to five, but Karl Deeter of Irish Mortgage Brokers says banks are querying how they operate within the scheme.
"What the banks haven't been able to do is ensure their systems are working in a way that interfaces with this (scheme)," he said.