A disagreement with a colleague: I say "What measures are your company currently implementing?"; she says "what measures is your company currently implementing?". It seems obvious to me I am right! Help!
What measures are your company currently implementing?
If are sounds better than is to your ears, I don't think that's necessarily because you're confused as to whether the grammatical subject is what measures or your company.
This is because you wouldn't think these sound right:
*What measures are it currently implementing?
*What measures are he currently implementing?
So for those who find are sounding better than is in the original text, the problem arises solely from the question of whether to treat your company as singular or plural.
Let's make it a declarative sentence to tease out the treatment of your company:
Your company is/are currently implementing these measures.
If you find are sounding better here, then your choice of are in the original text is not a mistake or confusion on your part. It's just that your dialect is that way.
If, however, you find is better here, then your choice of are in the original text is a mistake or confusion on your part.
There are several issues here, both grammatical and psychological that are getting conflated. First, what is the subject? I think most will agree that company is the subject but it can be confusing when we use the verb to be. After all, there is very little semantic difference between George is the teacher and the teacher is George. Since what measures has been brought to the front (regardless of whether it is the subject or not) then there is room for confusion. The sentence is not far from What measures are they that your company is/are currently implementing?. Because this is semantically close it easy for our brains to accept that measures is the subject.
Then, even if we accept company as the subject there is the question of whether it is singular or plural. Words that represent more than one person (and several beginning with co- such as company, council and couple) are often treated as plural even though they are grammatically singular.
However there are some psychological reasons that encourage the use of are. One is that measures are is, for obvious reasons, far more common than measures is and so our brains will tend to favour this form. The other is known as 'attraction', the habit our brains have of making words agree with the nearest one rather then the correct one.
Thus while the 'correct' answer may be is, there is a number of reasons, varying in validity, why our brains might choose are in this example.
As stated in the comments and other answers, according to the grammatical rule of subject-verb agreement, the use of "are" and "is" in a sentence like this should be based on the grammatical number of "your company", because that is the subject of the sentence.
Based on this, it is clear that "is" is acceptable: "company" is singular in form, and therefore can take singular agreement.
Although it not so clear that "are" is wrong, I would advise against using "are".
The only grammatical justification for "are" would be the phenomenon of "notional agreement" (agreement according to the meaning of a word/phrase, as opposed to "formal agreement", which is agreement according to the "form" of a word). But I don't think that plural notional agreement is particularly likely in this case.
"Notional agreement" with companies is supposedly uncommon in American English. (See the answers to Does "staff" take a plural verb?) I'm an American English speaker and this seems a bit of a simplification to me, but nevertheless, it seems to be a commonly repeated guideline. You don't say what variety of English you are using, but since formal agreement is acceptable in all varieties of English, that seems like a safer choice.
"Company" does not clearly have a plural meaning in this context. You can think of the company as being composed of multiple people, but the action of "implementing measures" is collective, not distributive. Implementing measures is something that the company does as a whole.
As an empirical matter, plural agreement doesn't seem to be common with "company". Here is a relevant Google Ngram Viewer chart:
This is for British English, the variety where notional agreement is supposed to be more common. The chart indicates that the frequency of "the company is" is much greater than the frequency of "the company are", and a substantial portion of the occurrences of "the company are" seem to be in the context "of the company are", where it is probably preceded by a plural noun (e.g. "the employees of the company are" or "the directors of the company are").