How to do if the company found out that the actual sale invoice amount is not correct after they submit VAT PP.30 for that month?

The company issued 1st sale invoice and submitted the VAT PP.30 already. After one month, the company found out that the price on the sale invoice is not correct and then they issued the new sale invoice with the new correct price, which such correct price is lower than the 1st sale invoice. In this case, the company need to submit an additional VAT PP.30?

Panwa : Yes, the company must submit the additional VAT PP.30 (price difference) for the over-declared sales and the company can request a Tax Refund. If you need further assistance for monthly tax filing, half year tax filing and doing yearly tax, kindly note that we could assist for such, click here. 

For more information, please feel free to contact us:
Phone: +66 2 933 9000
Fax: +66 2 933 6120
Email: bkk@panwa.co.th

For more information, please feel free to contact us:

Office: +66 2 933 9000
Whats'App: +66 8 5713 1000
Email: bkk@panwa.co.th

Location: https://goo.gl/maps/MhJsbjkPrji51Qyt6
Sky train: Yellow Line, Chokchai 4 Station, Gate 4. Our office is located between Soi Latphrao 50 and 52.

Address: 1560 Latphrao Road, Wangthonglang, Bangkok 10310, Thailand.