Tithe and Retirement

Biblical scholars, believers, and theologians; tax time has made me think of something related to tithes and offerings. I would be interested in other points of view and thoughts about the subject at hand.

From the time I began to faithfully tithe on a regular basis, I decided that I would base my tithe on gross salary and not net. This relieves me of having to worry about additional tithes if I receive a tax refund, or perhaps reducing my tithe if I had to pay additional taxes. Since I pay my tithes according to my gross salary, I have already tithed against any amount of a tax refund. I may choose to offer more with a tax refund, but my conscience is clear if I do not.

That is all fine for now, but I have started thinking about retirement. If most of my retirement is self-funded, is it the same as my tax refunds? I realize I will have to account for interest, dividends, and amounts matched by employers. But will I have clear conscience in not offering a full tithe in my retirement years? Something to ponder as retirement starts getting closer.