A tithe is 10 percent, and the Church upholds the biblical teaching that tithing is a command instituted by God for doing His work and caring for His Church.
Deuteronomy 14:22 Deuteronomy 14:22You shall truly tithe all the increase of your seed, that the field brings forth year by year.
American King James Version×teaches, “You shall truly tithe all the increase of your grain that the field produces year by year” (emphasis added). Based on this clear and direct biblical guideline, we see that we should calculate our tithe based on our “increase.” Increase is determined by any profit or earning we receive after we have subtracted the cost of doing business or the cost of investing in any work or investment activity.
If you receive a free gift, you need not pay tithe on it. That includes an inheritance. It is not necessary to give a tithe on a gift or any form of gratuity for which you do not perform some type of service. However, it would be appropriate to show thanks to God by giving an offering for having been blessed with a substantial gift.
Regarding the subject of inheritance, while it is discussed in a number of places in the Bible, tithing on an inheritance is referred to in only one place—in regard to the Levites. The tribe of Levi received tithes of the other tribes of Israel as an inheritance (Numbers 18:26-27 Numbers 18:26-27  Thus speak to the Levites, and say to them, When you take of the children of Israel the tithes which I have given you from them for your inheritance, then you shall offer up an heave offering of it for the LORD, even a tenth part of the tithe.
 And this your heave offering shall be reckoned to you, as though it were the corn of the threshing floor, and as the fullness of the wine press.
American King James Version×). Then the Levites were to tithe on that inheritance to the high priest (Numbers 18:28 Numbers 18:28Thus you also shall offer an heave offering to the LORD of all your tithes, which you receive of the children of Israel; and you shall give thereof the LORD’s heave offering to Aaron the priest.
American King James Version×). However, the sense of the term in this case concerns an entire tribe’s allotment among the tribes of Israel, the Levites having received no land when it was divided among the others. And the Levites worked for that inheritance, being assigned to duties in Israel’s worship system, just as the high priest also worked. And consider that the Levites were commanded to pay a tithe of the tithe—but not of the people’s offerings or gifts.
Thus, even including that specific instance with the Levites, all tithing had to do with what an individual labored for—the increase from gleaning grapes (and producing wine), olives, barley, wheat and the like, to harvesting fruit from orchards, to the increase from year to year from cattle, sheep, goats, etc. We find no specific command given to the children of Israel, or to the Church, to pay tithes on an inheritance or any other gifts.
Again, however, a thank offering for an inheritance or other substantial gift could and perhaps should be considered. But such an offering and the amount given is totally up to the recipient of the gift.