TDSR is calculated based on: your (monthly instalment) divided by (monthly gross income). According to the new guideline, banks will only lend if the TDSR < 60%. Monthly instalment shd include instalment for housing loan, car loan, personal loan, credit card outstanding etc. For monthly income, both fixed and variable income will be considered. But for variable income, banks are not considering 100%. Based on your example, with a monthly instalment at 180% of monthly income, the person's the monthly cashflow is negative. This means this person will not qualify for any new bank loan. Is this what you are asking?