In Payables, You can set tolerance for Purchase Order Matching and Tax Override.
Purchase Order Matching/Invoice Tolerances
Use the Invoice Tolerances window to define the matching tolerances you want to allow for variances between invoice, purchase order, and receipt information. You can define both percentage-based and amount-based tolerances.
If you enter a zero for a percentage tolerance and enable the check box for that tolerance, Payables will not allow any variance at all. If you want a low tolerance, you can enter a very small percentage. If you enter no value, then Payables will allow infinite variance. If you enter an amount-based tolerance, enter all amounts in your ledger currency. If an invoice exceeds these tolerances, Invoice Validation will apply a hold to it.
Navigation Path: Payables->Setup->Invoice->Tolerances
Tax Tolerances
Tax tolerances are used to determine whether E-Business Tax places a tax hold on an invoice due to the
override of calculated tax lines.
A tax tolerance is the acceptable variance between the calculated tax amount on an invoice and the override tax amount entered by the user. If the variance between these two amounts exceeds the tolerances you specify, then E-Business Tax places the invoice on hold. To define tax tolerances, you must first set the Allow Override for Calculated Tax Lines option.
Navigation Path: Payables->Setup->Options->Payables Options->Invoice->Tax Tolerances