The SNP recorded a deficit last year of around £320,000, according to official accounts lodged with the Electoral Commission.
Income rose to over £5.2m in 2019, but expenditure increased to £5.6m.
Spending on legal fees increased to £156,483.
The Commission’s website states that the SNP’s accounts were submitted in June this year.
It shows party membership standing at 125,691 by the end of 2019, which the document says represents 3.2% of the Scottish electorate.
The year covered by the accounts, 2019, included elections to the European Parliament and Westminster.
Income rose from £4.7m in 2018 to £5.2m, within which membership income remained roughly the same at £2.2m.
Donations also increased during the same period from £323,936 to £904,695.
However, expenditure rose from £3.6m in 2018 to £5.6m last year, with campaigning costs increasing from £287,056 to just over £1.5,
The party recorded a £319,161 deficit last year, unlike in 2018 when it was a £1.1m surplus.
Legal fees rose from £38,676 to £156,483.
Internal critics of SNP leader Nicola Sturgeon believe party headquarters lacks accountability and have called for reforms.
The SNP chief executive is Peter Murrell, who is Sturgeon’s husband.
An SNP spokesperson said: “The SNP rely on the commitment and generosity of our supporters to keep us campaigning.
“We have huge underlying financial strength, thanks to our mass membership. Last year we were able to allocate £1.4 million at short notice to contest unplanned elections.
“This included a General Election where the SNP won a landslide in Scotland, our best European election result ever, plus the parliamentary by-election in Shetland.
“We are immensely grateful to all our members and supporters who made those achievements possible in 2019.”
