Please be more specific. See Rule #2.

Hi Alan, Sami is correct. However; In Microsoft Access, Error 3201 typically occurs when a user attempts to add or change a record, but a related record is required in a linked table. This is a common data integrity issue, often triggered by a missing primary key or a foreign key constraint violation. For example, the error message "You cannot add or change a record because a related record is required in table '|'" indicates that a record cannot be saved in a child table without a corresponding record in the parent table.
This can happen during form operations, such as when trying to save a record in a parent form before adding related records in a subform.
Solutions involve ensuring the required parent record exists before attempting to save the child record, potentially using VBA code to save the parent record first.

Check the subform properties to see how/if it is linked properly.  HTH John

Hi Sami and John
Thanks for your replies
I am setting up a Tyre Use Database

You take the tyre into tyrestock table. Primary Key = TyreID.
The tyre is fitted to the vehicle on the tyrefitment table. Foreign key = TyreID.

My Main Form is unbound, to enter kilometres and reason tyre was removed from vehicle (TyreFitment Table) No additions or deletions allowed on Main Form. Only changes to the record. (Update Query)
Record updates and are saved in the TyreFitment table.

When I pressed tab on last entry on Main Form. I receive Error message You cannot add or change a record because a related record is required in table 'TyreStock" Please note TyreID (primary key from TyreStock table) was selected from combo box in my Main Form
I press Okay.

I can then enter information onto my bound sub form, to enter new record in my tyrefitment table, Record updates and saves in table.

Please note both forms update and records are saved.

Thanks.