Period & is not open for account type & and G/L & in company code &.

What causes this issue?

Period of fiscal year does not exist in table T001B either in period 1
or in period 2 of a table entry with record type "0", the selected
company code, the account type and the G/L account . The period is
therefore not open.

System Response

You can't continue processing.

How to fix this error?

Check table T001B for record type "0", the selected company code,
account type and G/L account . If required, please make an entry in the
table or change an interval.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.