Retail outlets, banks, schools, pubs and many other businesses will close for tomorrow's National Day of Mourning.
Major retailers including Tesco, Superquinn, Dunnes Stores and Boots said they would close all outlets.
Hoteliers and publicans have indicated they will shut for the day except to cater for essential functions.
The Government decision to hold a day of mourning was welcomed by most organisations, although concern was expressed by employers' groups about possible financial losses.
ISME, the small business association, called in vain for Sunday to be a day of mourning instead "as a form of compromise".
In a statement, the organisation said it "empathises with the objectives of the Taoiseach and the Government but the commercial realities [for] a significant number of small businesses should not be overlooked".
The Small Firms Association said all businesses which are in a position to honour the day of mourning should do so. However, it said: "Businesses with uninterruptable processes or those providing emergency services will not be expected to close." Those working in such companies, the association said, should not seek compensation or redress but rather "honour the many thousands of dead by conducting a minute's silence".
Echoing this point, IBEC, the employers' organisation, said it respected the Government's decision to declare a national day of mourning but noted it was concerned that continuous process industry and essential services continued to operate as normal.
"Every effort must be made by management and employees to limit the effects that any stoppage of work will have on such services and processes," IBEC said in a statement.
RGDATA, the small grocers' association, said it expected most shops would be closed tomorrow. "Some shops may open for a short period to provide essential services and facilities such as milk, bread and newspapers but I expect that most of the trade will shut down," said the RGDATA director general, Ms Ailish Forde.
Both the Irish Co-Operative Organisation Society and the Associated Craft Butchers of Ireland, representing family butchers, said they had advised members to close as a mark of respect.
Meanwhile, the Irish Congress of Trade Unions and SIPTU have called on workers throughout the country to support the day of mourning. The trade union IMPACT said it was closing its offices as a mark of respect.
Bank of Ireland and AIB both said they were closing, and other financial institutions are expected to follow suit.
The Vintners' Federation of Ireland said it was advising its 6,000 members to make arrangements, where possible, to close their businesses.
A spokeswoman for the Licensed Vintners' Association said it had advised its 700 Dublin members likewise. However, she said, "There might be certain functions which will be difficult to cancel, and it will be up to each particular publican to decide." The Irish Hotels Federation advised its members to respect the day of mourning and close where possible.
An Post said all post offices would be open until noon for the payment of pensions and benefits. Normal mail deliveries will take place to ensure benefits and payments reach their destinations.
Also staying open will be Dublin, Cork and Shannon airports.
Iarnr≤d Eireann said it would be making changes to its schedules. DART services will be reduced to a Sunday timetable.
All courts will be closed for the day. No tolls will apply on the East-Link and West-Link bridges between midnight tonight and midnight tomorrow. The Irish Times will be treating tomorrow as a designated public holiday.
The company's offices will be closed for business and public holiday arrangements will apply. The Irish Times will be published tomorrow and Saturday to keep readers informed of news developments.
The Government said people can get information on the day of mourning from the Employment Rights Information Unit at lo-call 1890 201 615 or 1890 220 222, or (01) 631 3131.