https://selling-guide.fanniemae.com/sel/b3-6-05/monthly-debt-obligations#P3441

If a monthly student loan payment is provided on the credit report, the lender may use that amount for qualifying purposes. If the credit report does not reflect the correct monthly payment, the lender may use the monthly payment that is on the student loan documentation (the most recent student loan statement) to qualify the borrower.

If the credit report does not provide a monthly payment for the student loan, or if the credit report shows $0 as the monthly payment, the lender must determine the qualifying monthly payment using one of the options below.

• If the borrower is on an income-driven payment plan, the lender may obtain student loan documentation to verify the actual monthly payment is $0. The lender may then qualify the borrower with a $0 payment.

• For deferred loans or loans in forbearance, the lender may calculate

• a payment equal to 1% of the outstanding student loan balance (even if this amount is lower than the actual fully amortizing payment), or
• a fully amortizing payment using the documented loan repayment terms.

https://guide.freddiemac.com/app/guide/section/5401.2

Student loans in deferment, forbearance or repayment, including income-driven repayment plans

In all cases, an amount greater than zero must be included in the monthly DTI ratio for all student loans, as described below:

• If the monthly payment amount reported on the credit report is greater than zero, the Seller must use the amount reported on the credit report, unless other documentation in the Mortgage file supports a different current payment amount greater than zero, or
• If the monthly payment amount reported on the credit report is zero, the Seller must use 0.5% of the outstanding loan balance, as reported on the credit report, unless other documentation in the Mortgage file supports a different current payment amount greater than zero

For student loans in income-driven repayment plans when documentation in the Mortgage file indicates the Borrower must recertify their income and/or that the Borrower’s payment will increase prior to or on the first Mortgage payment due date, the Seller may not use the monthly payment amount described above in the DTI ratio and must instead use:

• The greater of the current payment or 0.5% of the outstanding loan balance, or
• The documented future payment amount if greater than the current payment, or
• The future payment amount that is less than or equal to the current payment, provided that the Mortgage file contains documentation that the Borrower has recertified their income and the future payment amount has been approved. The future payment amount must be greater than zero.

https://www.hud.gov/sites/dfiles/OCHCO/documents/2021-13hsgml.pdf

For outstanding Student Loans, regardless of payment status, the Mortgagee must use: 

• the payment amount reported on the credit report or the actual documented payment, when the payment amount is above zero; or 
• 0.5 percent of the outstanding loan balance, when the monthly payment reported on the Borrower’s credit report is zero.

https://www.benefits.va.gov/HOMELOANS/documents/circulars/26_17_23.pdf

a. If the Veteran or other borrower provides written evidence that the student loan debt will be deferred at least 12 months beyond the date of closing, a monthly payment does not need to be considered. 

b. If a student loan is in repayment or scheduled to begin within 12 months from the date of VA loan closing, the lender must consider the anticipated monthly obligation in the loan analysis and utilize the payment established in paragraph (1) or (2) below. Calculate each loan at a rate of 5 percent of the outstanding balance divided by 12 months (example: $25,000 student loan balance x 5% = $1,250 divided by 12 months = $104.17 per month is the monthly payment for debt ratio purposes). 

(1) The lender must use the payment(s) reported on the credit report for each student loan(s) if the reported payment is greater than the threshold payment calculation above. 

(2) If the payment reported on the credit report is less than the threshold payment calculation above, the loan file must contain a statement from the student loan servicer that reflects the actual loan terms and payment information for each student loan(s).

https://www.rd.usda.gov/files/3555-1chapter11.pdf

For outstanding student loans, regardless of the payment status, lenders must use: 

• The payment amount reported on the credit report or the actual documented payment, when the payment amount is above zero; or 

• One half (.50) percent of the outstanding loan balance documented on the credit report or creditor verification, when the payment amount is zero.