State budget writers agreed Monday to build fiscal year 2020 budget plans on the assumption that state tax revenues will grow by 2.7 percent over the current fiscal year.

Gov. Charlie Baker’s budget chief and the leaders of the House and Senate Ways and Means Committees detailed a finalized accord on how much tax revenue the state expects to collect in fiscal year 2020, which begins on July 1. Budget watchers also upgraded their expectations for tax revenue in fiscal 2019, upping the projected total revenue by $200 million, to $28.529 billion.

The estimate of just under $29.3 billion in tax revenues for fiscal 2020 amounts to $770 million more in revenue than the updated projection for the current fiscal year. The projected growth rate will serve as the basis for Baker’s budget, which is due on Jan. 23, and budget-building exercises this spring and summer in the House and Senate.

Economic experts who offered their financial forecasts at the annual consensus revenue hearing earlier this month predicted state revenue collections will grow somewhere between 2 percent and 3.4 percent in fiscal 2020.

In announcing the agreed-upon revenue figure of 2.7 percent, budget officials used words like “modest” “more moderate,” and “responsible” to describe the forecast of the state revenue picture that represents a slowdown from the 3.5 percent revenue growth the officials had agreed to for the current year.

Fiscal 2018 tax collections of $27.787 billion surged 8.3 percent above fiscal 2017 collections, according to state records.

The slowdown in natural revenue growth comes as lawmakers re-evaluate plans for major increases in education, transportation and health care spending, and ways to pay for those investments. Legislative leaders have not ruled out tax increases in the new year and any proposals to raise taxes would be considered as part of the annual budget debate over the first half of 2019.