Income tax payments in April helped shrink the federal budget deficit, but the monthly surplus was less than a year ago, leaving government red ink so far this year 24.6 percent higher than 1987, the Treasury Department said Friday. The April surplus of $13.9 billion, representing the difference between what the government took in and what it spent last month, helped hold the deficit for the first seven months of the fiscal year to $105.0 billion. But that figure was much higher than the $84.3 billion in red ink during the first seven months of fiscal year 1987, when the total annual deficit eventually amounted to $150.2 billion. Economists say the April report indicates the Reagan administration will have a tough time meeting its goal of a $146.7 billion deficit for fiscal 1988, which ends Sept. 30, or even the Congressional Budget Office projection of $157 billion. Michael K. Evans, head of an economic forcasting service in Washington, said the April report indicates the deficit for the year will be between $170 billion and $175 billion. ``April's the big month. After that, it's all arithmetic. ... The belief that it was going to stay below $150 billion was just pure fiction,'' he said. The 1988 deficit target in the Gramm-Rudman deficit-reduction law is $144 billion. Budget Director James C. Miller III warned Congress on Tuesday that an across-the-board cut in federal programs, which would occur in October under the law, was ``perilously close.'' The April surplus, bolstered by $53.3 billion in individual income tax payments, was about $5 billion less than expected by private economists. They had been waiting for the report to see what effect the new income tax law would have. Some had thought the new tax law would provide a small windfall. However, Evans said the average, median taxpayer enjoyed a tax cut. ``People who used deductions and shelters paid more than they did the year before, but the rank and file paid less,'' he said. April income tax collections were 25.8 percent less than the same month a year earlier, which was inflated by the rush to take capital gains in 1986 before the favorable rates on that kind of income disappeared under the new tax law. Personal income tax collections of $237.6 billion for the first seven months of the fiscal year are running 2.7 percent behind last year. However, that has been offset somewhat by corporate income tax collections of $50.6 billion, 8.4 percent greater than last year. In April, all government revenue totaled $109.3 billion, 11.0 percent lower than April 1987. Spending totaled $95.4 billion, 13.6 percent ahead of the same month a year earlier. For the first seven months, revenues totaled $522.1 billion, up 3 percent over 1987, while spending was $627.1 billion, up 6.1 percent from the same period a year ago. As usual, the largest spending categories in April were the military, followed by Social Security, other programs in the Department of Health and Human Services and interest on the national debt. Military spending totaled $26.1 billion last month and $168.4 billion for the fiscal year so far, up 6.3 percent from the same period a year ago. Spending for Social Security totaled $16.3 billion last month and $121.3 billion for the past seven months, up 5.7 percent from the same period in the 1987 fiscal year. Social Security is exempted from budget limitations under the Gramm-Rudman deficit-reduction law and most months has been showing faster spending increases than the other categories. The other programs in the Department of Health and Human Services, including Medicare and Medicaid, spent $15.7 billion in April and $93.2 billion so far this budget year, a 6.5 percent increase over 1987. Interest on the $2.5 trillion national debt totaled $14.9 billion last month and $120.1 billion so far this fiscal year, an increase of 9.5 percent over the same period last year.