In order to be counted as part of your home mortgage loan application, overtime must be consistent and able to be easily proven and documented. You would need to provide at least two years worth of tax returns on your overtime earnings. If you cannot provide a history of it that far back, then you might be able to get away with providing less documentation, but you would want to confer with your home mortgage loan company or lender first.
If you plan to do more overtime in the future on a consistent basis, this might be another reason to include it in your home mortgage loan application. This can provide steady income, which makes your application more grounded and financially sound.