Do student loans in deferment or income-driven repayment count against my mortgage DTI?

It depends on the loan program. Fannie Mae and Freddie Mac generally use your actual documented payment, including a $0 income-driven repayment amount if shown on your statement, which helps many recent graduates qualify. FHA historically counted a percentage of the balance even for deferred or $0-payment loans, though its rules have shifted toward using the actual payment if it is above zero. VA loans often ignore payments deferred at least 12 months. Because policies differ, ask each lender exactly how it treats your student loans before applying, since it can swing your approval. If a lender uses a percentage of your balance, shopping for one that uses your real payment can raise your buying power substantially.