Election Obligations & Standards Database
"The tear-off part of the ballot should not bear any serial number, while the counterfoil might have these numbers for control purposes."
International IDEA: International Electoral Standards: Guidelines for Reviewing the Legal Framework of Elections
, p. 72
International Electoral Standards: Guidelines for Reviewing the Legal Framework of Elections
Provided they allowed for consistency with other international obligations, safeguards may be used to diminish the potential for duplicate voting.
The system for balloting (paper, electronic, or otherwise) should ensure the secrecy of a voter's choice.