Newcastle had more than £34million sitting in the bank at the end of the last financial year, the club's full accounts have revealed.
The club announced record profits last month of £18.7million for the 2013/14 season, but the full accounts registered with Companies House on Monday show that £38.6million was transferred into Newcastle's bank account as a cash-flow sum - paying off a £4.5million overdraft and leaving £34.1million available.
The revelation has infuriated Newcastle fans who claim owner Mike Ashley has little ambition beyond remaining in the top flight and benefiting from the lucrative Premier League TV deals.
A protest, backed by the Newcastle United Supporters' Trust, is planned for Sunday with fans being urged to boycott the home match against Tottenham.
The protest comes with the Magpies having lost their last five Premier League matches, including a painful 1-0 defeat at north-east rivals Sunderland.
Mark Jensen, editor of online Newcastle fanzine themag.co.uk, said: "The accounts show that all this cash was generated and the question a lot of fans would ask (is) why was a significant portion of that not spent on team strengthening?
"The idea of a boycott has been building for a long time and you can't blame the fans, and I'm all in favour of it. It's a starting point where fans may feel empowered and make their feelings known.
"The frustrating thing for them is the money is there but the club won't spend it.
"Newcastle United are a club that should be in the top eight every season - that's the size of the club with the support base it has and the benefit of being a city with one club.
"We are going to fall well short of that this season and that equals failure in lots of fans' eyes.
"It seems that every transfer window the squad keeps weakening. People talk about Newcastle being a well-run business - that may be so in the short term but in the long term we have a squad which needs massive investment."
The accounts say owner Mike Ashley still has £129million in interest-free loans outstanding but the money in the bank means the club's net debt is down to £94.8million.
The accounts also reveal that £29.8million was spent on signings after June 30, with £12.6million coming in player sales - mainly from Mathieu Debuchy's move to Arsenal.
The reported income from player sales does not appear to cover the January departures of Mapou Yanga-Mbiwa and Davide Santon, whose sales brought in around a further £8million.
Newcastle's salary bill rose to £78.3million from £61.7million, a 27 per cent increase, but that was more than covered by the increase in income from the new Premier League television deal and sponsorship income - the ratio of wages to turnover dropped from 64 per cent to 60 per cent.
A club spokesperson declined to comment.
Newcastle United have risked more criticism from supporters for trampling on the club’s history by dumping pictures of Sir Bobby Robson, Alan Shearer and Gary Speed in a skip outside St James’ Park.