President Reagan's tax-simplification plan will retain limitations on deductibility of business meals, as proposed in the Treasury Department's original version, congressional sources said yesterday.

Reagan is scheduled to make final decisions on the tax-simplification plan in a meeting today with senior White House and Treasury Department officials. Administration officials said a number of major issues still were undecided.

White House spokesman Larry Speakes said Reagan is expected to submit the plan to Congress next week.

The limitations on business-meal deductions would prohibit a company from deducting more than $10 per person for a business breakfast, $15 for lunch and $25 for dinner, including tax and tip. The plan, as proposed in November, includes a one-year phase-in during which 50 percent of the amount over those limits could be deducted. Under current law, those expenses are fully deductible.

The restaurant industry, one of the few groups that has been lobbying to change the proposal, says a study made before details of the original plan were known found that restricting the deduction to half the cost of business meals would throw 140,000 people out of work the first year. The per-meal limits would be even worse, an industry spokesman said.

"Our concern is that the Treasury Department is singling out one particular form of business expense. They're not attacking other forms of advertising or other things done to build up good will," said Ron Sarasin, government affairs director for the National Restaurant Association.

In making the original proposal, the Treasury Department said demand for business meals and other business entertainment would decline. But limiting the deduction, as well as terminating deduction for such other business expenses as professional sports events, would merely equalize the price to the business and nonbusiness consumer, the proposal said.

"As a result, the price of such services and goods would also tend to decline, benefiting the typical citizen who is unable to obtain a subsidy for consumption expenditures by characterizing them as business expenses," the document said. It predicted no net change in employment in the restaurant industry on the grounds that demand for cheaper meals would increase.

It was not clear whether the new plan would cap deductible expenses for business travel or terminate the deduction for other business entertainment expenses, such as seminars on ocean-liner cruises and country club dues. Reagan expressed worry when the plan was released last November that curtailing the deduction for country club dues could harm people who make deals at country clubs.

It was also learned yesterday that the floor below which employer-paid health-insurance premiums would be taxed as income is smaller than originally thought. Sources said the first $10 a month would be taxed for an individual and $20 for a family. The original tax-revision plan called for taxation of health-insurance premiums above $70 a month for an individual and $175 a month for a family.