Here are the examples where zero articles are used:
This is a tenant’s notice which does not have to be in statutory prescribed form but there is an example of how such a notice could be worded at…. The s.26 request has to be in statutory prescribed form, an example of which is given at … The s.25 notice has to be in statutory prescribed form. An example of a hostile notice is given at…
Below are sentences, where ‘a’ is used:
The s.26 request must be in a prescribed form. The tenant’s proposed terms for the new lease must either be attached to or inserted in the schedule to the s.26 request. Both a ‘hostile’ and a ‘friendly’ s.25 notice must be in a prescribed form and pre-printed versions are available for use. If prescribed information is omitted, the s.25 notice may be held to be invalid.
To be honest, in the first group of the examples, I would used the indefinite article before 'statutory prescribed form'. I cannot understand why this expression is used with zero article, while the words 'in a prescribed form' use the indefinite article.
Would you please explain the reason for using zero article and indefinite article in the examples and whether meaning is different?