You can split costs through Recurring Entries in Odoo. Go to Accounting >Periodic Processing > Recurring Entries. Start by creating a Model according to your needs (see the example below). You can use the variables in the Model's name. When generating the entry, Odoo will fill these variables according to the creation date. If you generate it in July, %(month)s will be replaced by 07.

If the amounts will be the same every time the recurring entry will be created, you can add them to the Model. If they change, you leave the amounts to 0 in the Model and you update them in the Draft Entry.

Now go to Define Recurring Entries. Create a new recurring entry and link it to your Model. Set the starting date and the frequency to generate the entries, i.e. each month during one year. Compute the lines to generate the posting proposals.

You can remove the proposal by clicking the Remove Lines button if you want to change the frequency.

Odoo can now generate the draft entries for you. Simply click Generate Entries from the menu and select the date before which the entries available will be generated (that date will be checked with the date in the subscription lines). As soon as an entry has been created, it will be linked to the corresponding subscription line (with an * in front to indicate the draft state). Each entry will be created in a Draft state, to allow you to update amounts (or add extra accounts). 

When you confirm the entry, its number will be displayed in the Recurring Entries. No more entries will be generated for that date.