The Exchequer recorded a deficit of €7.6bn in April, up from €7.5bn at the same time last year.
The deterioration is down to increases in current expenditure.
Despite this, tax receipts in the month were 8% higher than expected, driven mainly by higher levels of income tax.
Taxes overall were 20.3% or €519m higher than in April 2020.
Cumulative tax receipts at the end of April were €16.1bn. This was €227m, or 1.4%, higher than expectations and €652m, or 4.2%, higher than the same period last year.
Income taxes in April were €2.1bn - €62m, or 3%, higher than expected and €243m, or 13%, higher than April 2020.
In a statement, the Department of Finance said some of this is down to the 'base effect' of comparisons with the first lockdown last year when taxes fell.
But the trend in income tax over the last six months "…point to strong fundamentals…", it added.
Expenditure to the end of April was €26.7bn.
This was €794m or 3.1% higher than expected and €2.3bn or 9.1% higher than the same period last year.
April is traditionally neither a strong month for corporation tax or for collecting VAT.
When sums set aside for the Covid Restrictions Support Scheme (CRSS) are included, corporation tax receipts were €862m, down €40m on last year.
VAT receipts were also ahead of target.
Exchequer figs show continuing impact of #COVID19 on our public finances. As we continue to borrow heavily to support incomes & businesses through the pandemic, expenditure continues to rise. Tax receipts however bode well for recovery. Full details here https://t.co/UDqFlfKseV pic.twitter.com/VflBVLLpp5— Paschal Donohoe (@Paschald) May 5, 2021
Cumulative VAT to the end of April was €4.7bn, up €459m or 10.9% ahead of the same period last year.
Excise duty was 10.1% or €44m ahead of target in April. It is up €176m or 56.9% on April 2020.
Excise receipts fell substantially at the start of the pandemic so the year-on-year jump reflects the recovery since.
On a twelve month rolling basis, the Exchequer deficit in April was €12.5bn.
The department believes this gives a better indication of the trend in the public finances.
In 2020, the Exchequer deficit was €12.3bn.