Responsa for Bava Metzia 196:9
שאלה בשכירות ודאי לא שייכא או דלמא כיון דשייכא במקצת כמאן דשייכא בכולה דמי
<b><i>MISHNAH</i></b>. IF A MAN BORROWS A COW, AND HE [THE LENDER] SENDS IT TO HIM BY HIS SON, SERVANT OR AGENT; OR BY THE SON, SERVANT OR AGENT OF THE BORROWER, AND IT DIES [ON THE ROAD], HE IS NOT LIABLE. BUT IF THE BORROWER SAID TO HIM, 'SEND IT TO ME BY MY SON, SERVANT, OR AGENT,' OR 'BY YOUR SON, SERVANT OR AGENT, OR IF THE LENDER SAID TO HIM, 'I AM SENDING IT TO YOU BY MY SON, SERVANT OR AGENT,' OR 'BY YOUR SON, SERVANT OR AGENT, AND THE BORROWER REPLIED, 'SEND IT,' AND HE SENT IT, AND IT DIED [ON THE ROAD], HE IS RESPONSIBLE. AND THE SAME HOLDS GOOD WHEN HE RETURNS IT.<span class="x" onmousemove="('comment',' If the lender instructs him to send it back, the borrower is free from the risks of the road, but not otherwise. ');"><sup>7</sup></span>
Teshuvot Maharam
A. Since the overlord keeps the community responsible for the deficiency caused by the loss of C's pledge, the community is collectively held responsible for the entire tax (each individual, therefore, is responsible to the community and not to the overlord). Since C gave the pledge to the representative of the community, and it was lost while in the latter's possession, C is free from obligation. Therefore, the whole community must make up the deficiency. We can not compare this case to that of the man who betrothed a woman with a pledge (Kidd. 8b), and conclude that since the pledge was given as security only and did not constitute actual payment, that C did not as yet discharge his obligation; for the community is not obliged to pay the overlord actual cash, but may pay its tax in valuables as well as in cash. Thus the custom is that when a person gives a pledge to the community treasurer (and then fails to redeem it) the pledge is not sold but is handed over intact to the overlord's messenger, when the latter comes to demand the tax-money, in payment of that person's share of the tax, whether the pledge be worth much more than, or exactly as much as, that share of the tax. Therefore, whether a person pays cash or gives a pledge, makes no difference to the community. The second case you ask about, is exactly similar to the first. As soon as a person hands over his payment to the treasurer of the community, he is free from obligation. However, such payment must actually be made to the treasurer; mere setting aside of valuables as payment for taxes, is not sufficient.
SOURCES: Am II, 139.