Ireland: a multiple of income, set by the Central Bank
Ireland does not qualify borrowers on a debt-to-income ratio. The Central Bank's mortgage measures cap the loan itself at a multiple of gross annual income: four times for a first-time buyer, and three and a half times once you have owned a home before. Those limits are the same at every bank, because the Central Bank sets them rather than each lender.
Each limit carries an allowance. Up to 15% of a lender's first-time-buyer lending, and 15% of its second-and-subsequent-buyer lending, may be written above the multiple. An exception is therefore possible but rationed, and banks tend to spend the allowance on the strongest applications rather than the ones closest to the line.
Your existing debts still matter, but through a different door. They do not reduce the cap, which depends only on income; they reduce what the lender's own affordability assessment will actually offer you inside it. That is why the ratios on this page are shown as a guide here rather than a verdict: nothing in the Irish rules asks whether your total debt payments are 35% or 40% of income.
Worked example: €70,000 gross, first-time buyer
Four times €70,000 gives a ceiling of €280,000 on the loan. A second or subsequent buyer on the same income is capped at 3.5 times, or
€245,000, a €35,000 difference produced entirely by having owned before, with no reference to what either borrower already repays each month.