Policy regarding those eligible to handle sacred funds.

I remember being told once that only those who were full tithe payers were eligible to hold callings where they handle sacred funds (i.e. Bishopric and Clerks). I have looked in handbook one but can find no specific reference to this requirement. Does that requirement exist?

Although I can't find that specific wording in the handbooks, if you look in Handbook 1, Sections 13.3.2, 13.3.3, 13.4.2, and 13.4.3, you'll see that all clerks of any kind must be worthy to hold a temple recommend, which of course implies that they are full tithe payers. Regarding counselors in bishoprics and stake presidencies, it seems clear that anyone who has authority to give temple recommend interviews should meet the same requirements, although I can't find that requirement in the handbooks mentioned explicitly.

There was a 22 Sep 1999 letter about tithing faithfulness of clerks, but it was made obsolete by the publication of subsequent handbooks.

In any case, there is no doubt that the requirement you mentioned still exists.