The company said it would take a 250 million rand ($15.91 million) amortisation charge related to acquisition of Morocco's Saham Finances and 868 million rand in losses, mostly as a result of the consolidation of a special purpose vehicle related to a black economic empowerment transaction.
It had already flagged that the transaction would result in a 1.7 billion rand expense.
Black economic empowerment is part of a government drive to address inequalities still present after years of apartheid, and requires companies in South Africa to meet quotas in areas such as black ownership and procurement.
"Given the size of these items, headline earnings of the Group for the year ended 31 December 2019 are expected to decrease by between 15% and 25% compared to 2018," Sanlam said in a trading update.
Headline earnings would have increased by between 10% and 20% had it not been for these factors, it added.
Its shares were down 4.2% at 0956 GMT.
($1 = 15.7181 rand)
(Reporting by Emma Rumney; editing by David Evans)