The HSE will have a budget of €14.5bn next year, an increase of 3% on what it spent in 2017.
However, the HSE admits that some costs related to pay have not been factored in to their budget.
The Service Plan does not make provision for any extra staff, which unions say is imperative to improve services.
The Irish Nurses and Midwives Organisation says it expects that in order to fund pay increases under the Lansdowne Road Agreement, money will have to be diverted from other areas of the health service.
The INMO says it has serious concerns the HSE's budget will not provide for the required number of staff as the budget does not contain ring-fenced funding to pay increments as agreed under the pay deal.
The HSE has also been unable to recruit as many nurses as it planned to.
Phil Ni Sheaghdha, General Secretary designate of the INMO, said: "We're very concerned that what they will try and do is reduce staffing numbers in order to find that money, because we know we also have agreements that confirm that the nursing and midwifery workforce has to grow by a minimum of 1,300 whole-time equivalents in 2017.
"The HSE have not achieved that yet, we also know that the same number of growth will be required in 2018."