Has to be substantive in terms of content. Send to serials cataloger to confirm treatment. Serials cataloger will forward to monograph cataloger with a note that it came on serial standing order. Book record refers back to the serial record with a note and a 730 field on the book record that gives the name of the serial. In case of doubt about whether a piece should check in on the main record or not, please ask.
Some libraries actually like to treat the same type of situation differently.
An example of this is annual Buyer's guides or directories that constitute one issue every year of some periodicals, which can either get separate record treatment or check in on the main title. We'd rather see them than not see them, and need to make appropriate notes on records whichever way we decide to treat them.