Mr. Peter is being employed at our company as "Marketing Supervisor" as of 01.01.2010 till date with a monthly salary of 0000.0000
It's just about grammatical if it means that Mr Peter has only just been engaged. If he's already been working there for some time, you need to say 'Mr. Peter is employed at our company . . .'
Your sentence would read better if written as follows:
'Mr. Peter has been employed at our company as "Marketing Supervisor" from 01.01.2010 to date, with a monthly salary of 000.'
(Note: The 'from.. to..' could be British English, and the 'as of.. till..' American English).
Shebeer, your sentence is ungrammatical, as, in your understood intention to convey some timespan, you have wrongly mishmashed three temporal grammatical forms, one of which involves the preposition as of, another the construction from ... to, and the last one the preposition since.
As of(*) is never later in a sentence parallelled by to/till, because as of is used for situations whose truth is enduring, or more precisely, whose truth cannot later in the sentence be syntactically limited, e.g., by using function words such as to, until, for etc. (Semantically it can, of course: you can always add something like "it is falsely believed".) The structure as of + point in time (which point is allowed to be blurred) can be used in sentences such as these (quoted mostly from dictionaries):
- Darren terminated his job as of December 31st. The project was terminated as of January 1.
- As of last year, pupils are admitted according to where they live and go to school, and whether they already have siblings at the school.
- We begin work as of Tuesday.
- As of the moment, things are fine.
- As of next month, all the airline's fares will be going up.
(! Note that in the latter sentence the progressive aspect has special use. It will not happen that starting with the following month, the situation will be such that the action will be progressive—that the price of the fares will have increased on a certain day (commonly, the first working day of the month), then, that it will have increased some more later in the day, then some more the next day, and so on. Rather, the sentence means that the fares are set to increase once more. This use is different from the one in the op.)
You, also, wished to express the continuity of the situation stated, so you used a progressive aspect (in passive voice, but that's unimportant). You ought not to have additionally changed the default value of that grammatical category (a.k.a simple or Simple) for your verb; the preposition as of—in its interesting way—already denotes that the stated situation is not momentary. The preposition since is somewhat similar to as of, in that it denotes a more lasting situation. The similarity, to whatever extent, is only semantical, however. Syntactically, since conveys that the sitution is not momentary, by way of signalling and governing that perfect aspect (as required by standard English!) shall be used: They have been friends since childhood. She's been skiing since childhood. Dissimilarly to since, as of coexists quite fine with verbs having simple aspect.
So, you have mishmashed these three forms (I'll refrain from a more formal notation):
- is employed as of + past date
- was employed from + past date + to + endpoint less in past
- has been working since + past date
Additionally, you took till date ("date" meaning the time of the utterance) for your 'endpoint less in past', even though present perfect dispenses with the need for any temporal adverbial that means now such like "till date", which it does because a present perfect action implies that the endpoint less in the past is identical with the time of the utterance. Perhaps sensing this, you opted for present progressive, as it sort of resembles present perfect in that they never describe momentary situations. The result is a sentence of its own kind.
Therefore, a more grammatical sentence would be:
Mr. Peter is employed at our company as "Marketing Supervisor" as of 01.01.2010 with a monthly salary of 0000.0000.
See? Only a couple of words deleted. But for a reason.
Still, the sentence is yet to be free of any grammatical errors, to my mind. I think the use of at with employed is incorrect in a sentence written from the perspective of the employee's employer. A detached observer will commonly use the collocation employed at, but the employer should use something less detached, such as by and with (again, in my opinion). Please read through this (cf He is employed, with a friend, at the local Burger King.) and this.
So, I propose the correct version is:
Mr. Peter is employed by our company as "Marketing Supervisor" as of 01.01.2010 with a monthly salary of 0000.0000.
(*) That it is examined in Business Dictionary more carefully than in a number of other commonly used dictionaries, is illuminating as to whence this preposition came. In that light, the date of its first recorded use (1900) also suggests it's a term of business/legal register that later seeped into less formal registers, to wich as of today, for example, belongs.