The council has said it is 'extremely unlikely' that any further partner contributions will be secured, so the money will need to be taken from contingency budgets elsewhere.
The event is expected to have a total cost of around £778 million, with the council and other partners from the West Midlands expected to provide around £184 million of this.
Visiting the new aquatics centre on Thursday (20 January), the Secretary of state for sport brushed away funding concerns.
"The Government has put 75% of the funding in and I've been assured today that Birmingham City Council will be providing the other 25%" said Nadine Dorries.
But documents show that finding the extra money hasn't been easy for the council and it is facing a £25million black hole.
One paper reads: "the council's initial expectation was that partner funding contributions towards the council's (£184.2m) share of the cost of the Games would be secured to the value of at least £75million."
It continues: "Despite extensive engagement over a number of years at both political and senior officer levels, to date it has only been possible to secure partner contributions amounting to £50million."
The secured £50million funding comes from the West Midlands Combined Authority, The Local Enterprise Partnership for Greater Birmingham and Solihull and the Community Infrastructure Levy.
The council believes that, due to the pandemic and its impact on their finances, it's now 'extremely unlikely' that any further partner contributions will be secured.
It says the money will instead be made up from a contingency fund.
No matter where the funding comes from - the games will be coming to Birmingham in 6 months time.
"It's just amazing and I know it's going to be a great spectacle to come and watch the swimming here"
"It's absolutely incredible to be here at the Sandwell Aquatics Centre, the venue that's going to host the swimming event at the Birmingham Commonwealth Games" she said.
"Just to walk in and to see it, the venue, the water being in the pool, the diving blocks, the diving pool, the spectators, it's just amazing and I know it's going to be a great spectacle to come and watch the swimming here."