Fulfilled transactions, like a paid invoice, will not be synced to QuickBooks if it's outside a range which you can set in your sync preferences.
This does not mean the invoice doesn't exist. It still is retained in QuickBooks, however, it is not synced over. The reason for this is to improve sync times. For most companies, past transactions are not needed in day to day operations.
Note: Invoices with a balance greater than zero and sales orders that are not fully invoiced ignore this rule until they are paid off in full.
If you require to have your past transactions in Method:CRM, you can extend this range under Transaction History.
Note: Administrator permissions are required to access the QuickBooks Preferences.
Change Transaction History for All Transactions
1. Click the upper-right blue circle icon and then click Integrations.
2. Select QuickBooks Sync.
3. Click Expand on Advanced option.
4. Expand the dropdown for Maintain transaction history on Method for the past and select a time period.
Change Transaction History for One or More Transactions
1. Follow steps 1 to 3 to get to your QuickBooks Advanced preferences.
2. Select Edit history settings per transaction type:
3. This will open up a new page called History Per Transaction Type. Select a date range for each transaction you wish to keep the history for.