Help with grammar

[roman15]

I am writing a letter and i need to say i am enclosing two forms that are 288a's

I have written 'I also enclose two form 288a's to appoint ...'

Is this correct?

[squarebear]

288as as they are plural not possessive. You could say 288As to make it a bit clearer.

[squarebear]

Or what about "two 288a forms"?

[ivanerection]

what about putting i have enclosed the two relevant forms

[Quizmonster]

A strict grammarian would probably say, "I enclose two Forms 288a", giving the appropriate word an upper-case opening letter (capital F, in other words) and making it plural...Forms. A 'Form 288a' is, I presume, what one of these documents is called, so two of them would be Forms....it's not the 'a' that is plural.

[Quizmonster]

Perhaps I should have added the following to my earlier answer. The standard way to pluralise a single letter of the alphabet is to use - after the letter - an apostrophe followed by 's', which is exactly what you did in the actual question, Roman! Thus we find "Dot your i's and cross your t's"..."Mind your p's and q's"..."How many i's are there in 'Mississippi?" ...and so on.
So, if you prefer to use the sentence-format you started with rather than my very formal one, you should write:

I also enclose two Form 288a's.

(I'd still suggest a capital 'F', as Form 288a is effectively a 'title'.)