accrual account is not getting knocked off after matching to invoice

 Hello,

i have an issue on the accrual accouting for the expense item .

we are creating expense po with tax  ( UK VAT)  the po is created with 3 way matching, matching option is at receipt  and accrued at period end is checked .

we do the standard receipt . The tax amount is getting added to the item

the entry  while doing the receipt  is    charge account dr 120  and accrual account cr  120

when we create po matching invoice the accounting entry is

Accrual account is  Dr 100,

non recoverable tax  Dr 20

AP liability   account  cr     120

we noticed the accrual is not getting knocked off.