However, Mr Dunlop yesterday told lawyers representing the Swords councillor that this figure would "pale into insignificance" compared to corrupt payments he made to other politicians.
The inquiry has heard allegations that Mr Gallagher a former Eircom employee who died in March 2000 was paid £2,000 (€2,539) in cash by Mr Dunlop.
This was, it is claimed, for his support for a 1991 council motion to allow a hotel to be built on 90 acres of land near Swords, Co Dublin.
In an interview with tribunal lawyers before his death, Mr Gallagher stated that the most he had ever received from Mr Dunlop was £300 (€380) adding, "that is, if I did get it."
Under questioning by tribunal barrister Pat Quinn SC, Mr Dunlop said he believed the sum was included in an estimate of 3,000 (€3,809) that he had paid Mr Gallagher, at an unknown time in the early 1990s in relation to what are known as the "Duff lands".
Solicitor Giles Montgomery said there was not a scintilla of documentation to support Mr Dunlop's allegations against his client.
Mr Montgomery also pointed out that the witness had already been forced to apologise for two errors in his recollection of lobbying for the project.
Mr Dunlop apologised for having to make such claims about a dead man but insisted that Mr Gallagher sought money for his support on several controversial rezoning issues.
Mr Dunlop also admitted he was wrong to claim that he paid a £1,000 (€1,270) bribe to Fianna Fáil TD, G V Wright, in relation to the Duff lands during a private interview with the inquiry's legal team in May 2000.
He acknowledged he was "in error" over his recollection on this rezoning issue, but maintained that the Dublin North TD received payments from him in return for votes on a number of other planning matters during this period.
The inquiry has heard that Dublin jeweller Robert White engaged Mr Dunlop in 1990 to help secure the support of members of Dublin County Council for his plans to build a hotel near Swords.
Mr Dunlop said yesterday that he now accepted that Mr White had told him at the time that Mr Wright was "totally onside" and that the businessman would "look after" the politician.
"I understood that to mean some arrangement had been arrived at by way of financial arrangement or inducement between Mr White and G V Wright," said Mr Dunlop.
He refused to offer an apology to the TD on the basis that it was sufficient he had admitted his error.
The tribunal was adjourned until March 21.