Under Contract Law, does the residential tenancy agreement form have to be the standard form from the government? If I signed a form which is not the standard form, does it mean it is invalid?
The lessor cannot make a residential tenancy agreement containing terms or conditions which contract out of theResidential Tenancies Act 1987 (the Act). A tenant and lessor can agree to have clauses added as long as these don’t change the rights and obligations under the Act."
Therefore, while I cannot say for sure, I expect that if another type of written tenancy agreement is used, then to the extent it conflicts with provisions of the Residential Tenancies Act, it is invalid however the tenancy itself would be valid and would be supplemented with all the clauses provided for in the Residential Tenancies Act. For example your tenant would have all the rights set out in that Act, even if you do not write them in your tenancy agreement.