Social care workers in Wales have still not received a £500 cash bonus that was promised more than two months ago.
The health minister said the Welsh Government is "looking to exhaust every avenue" to persuade the UK government the bonus should not be taxed.
Vaughan Gething said "every penny" should go to social care staff and not be "a windfall for the Treasury".
The UK government said Welsh ministers had the power and funding to increase the payment to account for deductions.
More than 64,000 social care workers were told by First Minister Mark Drakeford on 1 May that they would get a cash bonus of £500, at a cost of £32.2m.
It was to recognise the fact residential and domiciliary care staff were "often accepting a greater degree of risk", Mr Drakeford had said.
In June, the pledge was extended to care home kitchen and domestic staff, agency and nursing staff, personal assistants working in care homes, and domiciliary workers.
But no payments have yet been made.
"It's deeply frustrating for not just the government but, in particular, for care home workers themselves," Mr Gething told the BBC Politics Wales programme.
"We're still trying to get the UK government to a position where they won't take tax and National Insurance off these payments."
Mary Wimbury, chief executive of Care Forum Wales, said even if workers got the bonus, it would "not be enough".
"We see the £500 as the first step to a long-term solution where the vital role care workers undertake is properly rewarded," she said.
"We cannot continue with local authorities and health boards setting fee rates that assume they will only be paid the legal minimum wage."
In a statement, the UK government said it had provided £2.3bn of funding for the Welsh Government to support people, businesses and public services during the pandemic.
"We are working with the Welsh Government to determine the exact scope of the proposed bonus," a spokesman added.
"Payments made in connection with employment are however chargeable to income tax and NICS unless explicitly exempt.
"The Welsh government has the powers and funding to gross up the payment, if its intention is for social care workers to benefit by at least £500."