Sikh Rehat Maryada on SGPC site mentions the method of giving tankhah
Method of Imposing Chastisement (Tankah)
Article XXV
a. Any Sikh who has committed any default in the observance of the Sikh discipline should approach the nearby Sikh congregation and make a confession of his lapse standing before the congregation.
b. The congregation should then, in the holy presence of Guru Granth Sahib, elect from among themselves five beloved ones who should ponder over the suppliant's fault and propose the chastisement (punishment) for it.
c. The congregation should not take an obdurate stand in granting pardon. Nor should the defaulter argue about the chastisement. The punishment that is imposed should be some kind of service, especially some service that can be performed with hands.
d. And finally an Ardas for correction should be performed.
As Sukhdeep Singh veerji pointed out that now a days we do not get the pooran gurmat managed Gurdwara sahibs and majority in the sangat themselves are non amritdhari. So in such scenario will it not be proper to ask the one who has not committed a bajjar kurehat but is still tankhayia due to dhill in rehat to attend the nearest amrit sanchaar samagam?
Also what is the limit of dhill that makes it mandatory to go pesh. Lot of singhs have given different version of what is and what not the dhill in rehat that requires mandatory peshi. Please provide more information.