RICHARD - I have a couple of questions on tithing. Can you please tell me if the current information as follows is current information as found in our current Church Handbook of instructions.
Have found this information on the web and want confirmation if this information is true with every iota-

1. Can you tell me which First Presidency sent a letter on March 19, 1970, On March 19, 1970, the LDS First Presidency sent a letter to presidents of stakes and missions, bishops of wards, and presidents of branches in answer to the question, What is a proper tithe?

"For your guidance in this matter, please be advised that we have uniformly replied that the simplest statement we know of is that statement of the Lord himself that the members of the Church should pay one-tenth of all their interest annually, which is understood to mean income. No one is justified in making any other statement than this. We feel that every member of the Church should be entitled to make his own decision as to what he thinks he owes the Lord, and to make payment accordingly."

The church's official General Handbook of Instructions quotes from this March 19, 1970 letter from the First Presidency as what sets forth a definition of what is tithed. Here is a portion of the General Handbook of Instructions from that section:

"The simplest statement we know of is the statement of the Lord himself, namely, that the members of the Church should pay one-tenth of all their interest annually,' which is understood to mean income. No one is justified in making any other statement than this." (First Presidency letter, 19 Mar. 1970; see also D&C 119:4).

Because the General Handbook of Instructions quotes the 1970 letter from the First Presidency, the 1970 letter remains the current official written policy on tithing.
The statement of the First Presidency on tithing is in complete harmony with canonized scripture. This is clear if one does a plain reading of the text in D&C 119:4-5. The phrase "one-tenth of all their interest annually, which is understood to mean income", has harmonious meaning with "one-tenth of all their surplus properties annually, which is understood to mean surplus income."

2. So as I understand, there is no information from our past prophets that we are to pay tithing on our net or Gross?

JOEL - The information that you now have in regards to tithing is true and has not changed.
The First Presidency which sent the letter you referred to was Joseph Fielding Smith and counselors Harold B. Lee and N. Eldon Tanner.
As you mentioned, in that letter it states that, notwithstanding the fact that members should pay one-tenth of their income, "every member of the Church is entitled to make his own decision as to what he thinks he owes the Lord and to make payment accordingly".
There have been no Church leaders that have stated as official interpretation of this doctrine that tithing means one-tenth of gross or net income, although some may have their own personal opinion about it. The reason for this is that there are too many different situations where it is hard to determine exactly what a person's gross or net income is, especially if they are farmers or business owners with a lot of overhead and other expenses. Many members with regular salaried jobs, trying to be as faithful as they can to the principle, will choose to pay on the gross. But people in countries with socialist programs, who pay a very large percentage of their wages to the government in taxes, would'nt have much money left to live on if they paid on the gross. Everyone must prayerfully decide for himself what he believes is a proper tenth of his income.