What is accrued interest in regards to suing somebody for money owed to you?
Even if a specific interest rate was not specified, one could still add a reasonable interest rate and presumably collect that additional amount when suing for collection of a loan (or monies owed to you). If a court is involved they might decide on the exact amount of accrued interest and whether that accrued interest amount will be collected in addition to the principle amount (the original loan amount).