Make a backup of your company. For instructions see related article below
Open 7-4 Rebuild Database and click start for all tables.
Open 1-6 Period/Fiscal Year Management and click the Change period button. Change period back to period 1 of the current year.
Answer Yes when prompted with “Do you ant to change the default posting period back […]

Resolution for '74 Rebuild Database issue: 'When changing the posting period on a new record. Error Continue Quit. Object reference not set to an instance of an object' available: Yes.

The 74 Rebuild Database issue or error code is a known related to Sage Accounting products. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the 74 Rebuild Database issue yourself by looking for a resolution described in the article. If it is a complex 74 Rebuild Database issue or you are unable to solve the issue, you may contact Sage Repair by clicking here or by using other 74 Rebuild Database support options.

For more information about resolving issues related to 74 Rebuild Database in Sage Accounting or to get support for the issue 'When changing the posting period on a new record. Error Continue Quit. Object reference not set to an instance of an object', click the link below: