Zakah (Arabic for: alms prescribed according to Islamic teachings) is the second pillar of Islam. It is incumbent on every male and female Muslims once they have the means to pay it. A Muslim does not need to tell the recipient that it is zakah because Islam is highly considerate about taking care of the feelings of all people,

[If you give alms openly, it is well, and if you hide it and give it to the poor, it is better for you; and this will do away with some of your evil deeds; and Allah is aware of what you do.](Al-Baqarah 2:271)

In addition, you are allowed to pay zakah for several future years if there is a need that justifies this.

Regarding the question of telling the recipient of zakat the kind of money he is being given and the payment of zakat in advance , Dr. Monzer Kahf, a prominent economist and counselor, demonstrated,

It is not a requirement of the Muslim Shari`ah to inform the recipient that what he or she is given is zakah. Rather, if telling it as zakah may be expected to hurt the feelings of the recipient, it is recommended that he or she not be informed.
Zakah can be given in kind as food items, household needs, cloth, transportation, and dwelling. One should make one’s best to give zakah to those who are in most pressing needs especially when the recipient is also a God-fearing person.

Lastly, it is not permissible to pay zakah for several years in advance, as zakah is a yearly obligation. But it is permissible to give it in advance for more than one year when there is a real need for it in advance.

The example, as the questioner meant it, is to spend a large sum with the intention of zakah even if it exceeds the amount due for the current year, to respond to a dire need of a recipient, a need for a dwelling or means of transportation that is direly needed, and then calculate the extra payment on accounts of future years of zakah. This means in future years, one would have already paid the required zakah and keep that calculation until the amount paid in advance is exhausted.