You should use (4, id) in the write method.

Ex:

for id in [4,5]:
    my_obj.write({'ur_m2m_field': [(4, id)]})

There are actually0-6 numbers for representing each job for a many2many/ one2many field

• (0, 0, { values }) -- link to a new record that needs to be created with the given values dictionary
• (1, ID, { values }) -- update the linked record with id = ID (write values on it)
• (2, ID) -- remove and delete the linked record with id = ID (calls unlink on ID, that will delete the object completely, and the link to it as well)
• (3, ID) -- cut the link to the linked record with id = ID (delete the relationship between the two objects but does not delete the target object itself)
• (4, ID) -- link to existing record with id = ID (adds a relationship)
• (5) -- unlink all (like using (3,ID) for all linked records)
• (6, 0, [IDs]) -- replace the list of linked IDs (like using (5) then (4,ID) for each ID in the list of IDs)

Hi, I am using Odoo 14 and Sudhir answer works, but it seems that Odoo is protecting itself because it gets back in a second to the original values. I am trying to link an invoice to as sale order, so I am using:

record.write({'invoice_ids': [(3, 456)]}) #456 is the record of the invoice
raise Warning(record.invoice_ids)

The warning shows that the new Id has been appended to the current values, but if I check again in the next second, the values get back to the original. Any clue on how to make them persistent?

Thx.