The Charity Commission is to contact the Professional Footballers' Association amid concerns about links between its charitable arm and the £2m-plus earnings of PFA chief executive Gordon Taylor.
The PFA Charity's latest accounts, for the year ending June 30 2017, say "the charity does not have any employees and therefore no salaries or wages have been paid during the year".
But the accounts also list staff costs of £3.8m, up from £3.2m in 2016.
They also detail expenditure of £325,000 on travel, £510,000 on office expenses and £235,000 on fees to investment managers.
The PFA pays staff through a PFA General Fund, which raises questions about the link between the fund and the PFA Charity.
Taylor received a total remuneration package of £2.2m in 2016/17, according to the PFA's own accounts.
A commission spokeswoman said: "We are aware of concerns regarding the expenditure of the Professional Footballers’ Association Charity and we will be engaging with the trustees to establish the facts.
"Trustees should be able to demonstrate that all decisions around expenditure have been carefully considered in line with the best interests of their charity and those it is set up to help.
"The public rightly expect charitable funds to go to causes they are set up to support. As regulator we expect all charities to carefully steward funds in the best interests of their charity in order to maximise their benefit to society."
All charities reporting under the Statement of Recommended Practice are required to disclose salaries above £60,000 in bands of £10,000, identifying the number of staff paid in each band.
The Manchester-based PFA, which represents professional footballers, has seen its income more than double over the past three years to £27.9m.
Its main source of income, Premier League TV revenue, is listed as a donation in its accounts.
It holds reserves of about £40m.
The PFA Charity's contact number on the commission website is the same as the PFA's.
Calls by Third Sector this morning were not returned.
The PFA's trustees include former footballers Garth Crooks, David Weir and Brendon Batson.