There's no one definitive answer to this question since it will vary depending on the mortgage lender, the terms of the mortgage agreement, and the state of the housing market. However, most experts agree that if you miss 3-6 mortgage payments in a row, you'll likely be facing foreclosure.
If you're behind on your mortgage payments, it's important to get caught up as soon as possible. Missed payments will not only lead to foreclosure but they will also have a devastating impact on your credit score and other related finances.
Contact your lender if you're having trouble making your monthly payment and see if there are any solutions available to you. You may be able to work out a modified repayment plan or even refinance your mortgage altogether. Don't wait until it's too late.