Most taxpayers have a reasonable continuity in their income from year to year. In other words, most people make similar amounts of money from one year to the next. There are certainly changes after promotions, raises, career shifts. Annual incomes can be drastically lower when a tax year includes a period of unemployment because of a rough economy, injury, or time taken off following childbirth. But by and large, if you earned $50,000 last year and haven’t changed jobs or taken time off from work, you can probably expect a similar amount this year.

There is one group of economic actors who cannot count on the same level of predictability. That group is comprised of the many Americans who grow and catch our food: farmers and fishermen. If an unexpectedly good year drives up profits, that year may be taxed at a much higher rate than typical years. Form 1040 Schedule J allows farmers and fishermen to average an income against lower incomes from the previous three tax years. Farmers and fishermen may elect to do this when it will lower their tax obligation in the current year. Farmers and fishermen, read on for a guide to lowering your tax obligation with Schedule J.

Oddly enough, you needn’t have been in the business of farming and fishing during any of the base years, and you may elect to average income even if your filing status was not the same in the election years and base years. To fill out Schedule J, you may need copies of your original or amended returns from the previous three years. You can request these from the IRS if need be, but there’s a $43 fee for each, unless your main home, place of business, or tax records are located in a federal disaster area. In that case, the IRS waives the fee.

Once you have all of those forms assembled, you can start filling out your Schedule J. You’ll begin by filling out this year’s income and elected farm income. You’ll then begin copying data from your previous forms to this year’s Schedule J. This process is, to be frank, a little intricate. You’ll copy different information from previous returns depending on how you filed in previous years. Using that data, you’ll calculate taxes on averages of this year’s income with previous years, using the rates from previous years.

While it may sound complicated, in practice it’s just a matter of copying amounts from one form to another. The Schedule J spells out precisely which lines to use from previous forms, and what operations to perform. The process is a little different for every filer, but it’s always spelled out on Schedule J. Provided you’re careful, it’s all a matter of following instructions. When you’re finished, you’ll arrive at a tax figure for this year. Needless to say, you should only elect to use this number if it is less than your tax obligation would be if you didn’t elect to use the Schedule J.

If this is a bad year and income was low, you may be better off without the Schedule J. If you’re at all wondering whether or not the Schedule J is a good idea, or if you’re confused about how to file your taxes, it’s best to consult a professional. A qualified accountant can make sure you follow all applicable laws, and lower your tax obligation as much as it can be lowered.

Should you need help filing your taxes this year, you may want to consider both Turbo Tax and H&R Block. Their free online tax software can make your tax nightmares disappear.

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Read More: What Is The Cheapest Tax Software