When you post a document, the system checks whether the periods determined can be posted to. You can specify which posting periods are open for posting in the system. You can have as many periods simultaneously open for posting as you like.
You can specify which company codes are open for posting independent of the company code. To do this, you use cross-company code variants for periods open for posting. You make specifications per posting period variant. You assign these variants to a company code.
This procedure is useful if you maintain a large number of company codes. Since you specify permitted posting periods only by variant, you define only one variant. You then allocate to this variant all company codes which are equally managed with respect to the permitted posting periods. See also
Opening and Closing Posting Periods.By specifying the account number, you can open posting periods for particular accounts.
You can define which periods are open by specifying one of two intervals.

As upper and lower limit, specify both a posting period and fiscal year. You close a period by selecting the period specifications so that the period to be closed does not fall within them.

In the current fiscal year, you want to be able to post data to your G/L accounts in the previous period, the current period, and the following period. You also want to be able to post data to a closing period in the previous fiscal year. The above graphic shows the entries you would make in the system assuming the current period to be 03/1992.
If you want to open posting periods for particular accounts, specify the periods for these accounts. You should always enter G/L account numbers in the system. For sub-ledger accounts, you define the permitted posting periods by entering the relevant G/L reconciliation accounts. Enter the appropriate account type.

You want to create the financial statements. You therefore want to limit the posting of data to the customer and vendor accounts to the current period and the following period. To do this, you enter the reconciliation accounts for the customers under account type D, and the reconciliation accounts for the vendors under account type K, along with the required periods. The current period is assumed to be 03/1992.

You also have to explicitly open the current period and any special periods for posting. You should maintain the permitted posting periods regularly at the end of each month closing those periods no longer needed and opening the new ones required.
It is also possible to control the permitted posting periods individually for each user by entering an authorization group at document header level (account type "+" = valid for all account types). This authorization group is effective only in time period 1 and affects users who do not have the appropriate authorization for the authorization object F_BKPF_BUP (accounting document: authorization for posting periods) by not allowing them to post in the periods that are open only for time period 1. Therefore, you can, for example, open certain periods for certain users only within the year-end closing.
For more information on user authorization, refer to the Implementation Guide for Authorization Management under Financial Accounting Global Settings.