The Charity Commission is investigating the Christian organisation after a digital accounting system introduced in April couldn't punctually process payments.
It's looking to establish whether regulatory advice or "other action" is required after the Salvation Army reported a serious incident.
A Salvation Army spokesman told the Mail on Sunday: "We want to take this opportunity to unreservedly apologise for the delay in some of our suppliers receiving payment for invoices and the added pressure this has had on some of our officers and staff."
A source from the Salvation Army told the newspaper workers had received hundreds of court demands and final pay demands because the unpaid bills were in their names - despite it being the charity's responsibility to pay them.
She reported: "Red letters are arriving every day. The officers are being pushed to the edge by the sheer stress of the situation.
"Some are so fed up with the financial pressure they are being put under that they even are thinking of leaving the Salvation Army."
In a leaked email sent to workers last month, Salvation Army trustee Lieutenant-Colonel Alan Read apologised, adding he was "horrified" to learn of disruption caused by the new accounting system.
The Salvation Army spokesman continued: "We recognise that as we strive for stringent accounting processes across the country, there have been issues that have slowed us down but we remain committed to accountability and fair business and we want to reassure people that we are taking all actions necessary to ensure smooth operations going forward."
Lieut-Col Read also revealed two senior Salvation Army finance officers had resigned on 11th August.
In the UK and the Republic of Ireland, the Salvation Army has 50,000 members, 4,000 employees and 1,000 officers (full-time ministers).