Farmers who received some government information late have been given additional time to file their 1987 federal income-tax returns. The Internal Revenue Service said Monday it was granting special relief to farmers who did not receive Agriculture Department documents by the Feb. 15 scheduled date. Those documents are Form 1099-G, which reflects certain government payments, and Form 1099-A, on which acquisitions or abandonments of secured property are reported. Farmers generally are not subject to penalties for underpayments if they file their returns by March 1. The IRS concluded that farmers who failed to receive required information from the Agriculture Department by Feb. 15 might be unable to meet the March 1 deadline. The IRS said farmers affected by the delay should attach to their tax return a Form 2210F on which they have written their name and Social Security number and, on the bottom right, the words ``farm waiver.'' With the extension, farmers will have to file returns and pay any tax owed by April 15, the deadline for most taxpayers.